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he license the mit license the gnu general public license gpl the bsd licenses the gnu lesser general public license lgpl and the mozilla public license mpl open source licenses are software licenses that allow content to be used modified and shared they facilitate free and open source software foss development intellectual property ip laws restrict the modification and sharing of creative works free and open source licenses use these existing legal structures for an inverse purpose they grant the recipient the rights to use the software examine the source code modify it and distribute the modifications these criteria are outlined in the open source definition osd after 1980 the united states began to treat software as a literary work covered by copyright law richard stallman founded the free software movement in response to the rise of proprietary software the term open source was used by the open source initiative osi founded by free software developers bruce perens and eric s raymond open source emphasizes the strengths of the open development model rather than software freedoms while the goals behind the terms are different open source licenses and free software licenses describe the same type of licenses 1 the two main categories of open source licenses are permissive and copyleft both grant permission to change and distribute software typically they require attribution and disclaim liability permissive licenses come from academia copyleft licenses come from the free software movement copyleft licenses require derivative works to be distributed with the source code and under a similar license since the mid 2000s courts in multiple countries have upheld the terms of both types of license software developers have filed cases as copyright infringement and as breaches of contract background edit main article history of free and open source software legal scholar eben moglen on the history of copyright intellectual property ip is a legal category that treats creative output as property comparable to private property 2 legal systems grant the owner of an ip the right to restrict access in many ways 3 owners can sell lease gift or license their properties 4 multiple types of ip law cover software including trademarks patents and copyrights 4 most countries including the united states us have created copyright laws in line with the berne convention with slight variations 5 these laws assign a copyright whenever a work is released in any fixed format 6 under us copyright law the initial release is considered an original work 7 the creator or their employer holds the copyright to this original work and therefore has the exclusive right to make copies release modified versions distribute copies perform publicly or display the work publicly modified versions of the original work are derivative works 8 when a creator modifies an existing work they hold the copyright to their modifications 9 unless the original work was in the public domain a derivative work can only be distributed with the permission of every copyright holder 10 in 1980 the us government amended the law to treat software as a literary work software released after this point was restricted by ip laws 11 at that time american activist and programmer richard stallman was working as a graduate student at the mit computer science and artificial intelligence laboratory stallman witnessed fragmentation among software developers he blamed the spread of proprietary software and closed models of development to push back against these trends stallman founded the free software movement 12 throughout the 1980s he started the gnu project to create a free operating system wrote essays on freedom founded the free software foundation fsf and wrote several free software licenses 13 the fsf used existing intellectual property laws for the opposite of their intended goal of restriction instead of imposing restrictions free software explicitly provided freedoms to the recipient 14 bruce perens author of the open source definition in the 90s the term open source was coined as an alternative label for free software and specific criteria were laid out to determine which licenses covered free and open source software 15 16 two active members of the free software community bruce perens and eric s raymond founded the open source initiative osi 17 at debian perens had proposed the debian free software guidelines dfsg 18 the dfsg were drafted to provide a more specific and objective standard for the foss that debian would host in their repositories 19 the osi adopted the dsfg and used them as the basis for their open source definition 20 the free software foundation maintains a rival set of criteria the free software definition 21 historically these three organizations and their sets of criteria have been the notable authorities in determining whether a license covers free and open source software 22 there is significant diversity among individual licenses but little difference between the rival definitions 16 the three definitions each require that people receiving covered software must be able to use modify and redistribute the covered work 23 eric s raymond was a proponent of the term open source over free software he viewed open source as more appealing to businesses and more reflective of the tangible advantages of foss development one of raymond s goals was to expand the existing hacker community to include large commercial developers 24 in the cathedral and the bazaar raymond compared open source development to the bazaar an open air public market 25 he argued that aside from ethics the open model provided advantages that proprietary software could not replicate 26 27 raymond focused heavily on feedback testing and bug reports 28 he contrasted the proprietary model where small pools of secretive workers carried out this work with the development of linux where the pool of testers included potentially the entire world 29 he summarized this strength as given enough eyeballs all bugs are shallow 30 the osi succeeded in bringing open source development to corporate developers including sun microsystems ibm netscape mozilla apache apple inc microsoft and nokia these companies released code under existing licenses and drafted their own to be approved by the osi 31 32 types edit see also comparison of free and open source software licenses open source licenses are categorized as copyleft or permissive 33 copyleft licenses require derivative works to include source code under a similar license permissive licenses do not and therefore the code can be used within proprietary software copyleft can be further divided into strong and weak depending on whether they define derivative works broadly or narrowly 34 35 licenses focus on copyright law but code is also covered by other forms of ip 36 major open source licenses written since the late 1990s contain patent grants these open source patent grants cover the patents held by the developers 37 software patents cover ideas and rather than a specific implementation cover any implementation of a claim patent claims give the holder the right to exclude others from making using selling or importing products based on the idea because patents grant the right to exclude rather than the right to create it is possible to have a patent on an idea but still be unable to legally implement it if the invention relies on another patented idea thus open source patent grants can offer permission only from covered patents they cannot guarantee that a third party has not patented any concepts embodied in the code 36 the older permissive licenses do not discuss patents directly and offer only implicit patent grants in their offers to use or sell covered material 38 newer copyleft licenses and the 2004 apache license offer explicit patent grants and limited protection from patent litigation 39 these patent retaliation clauses protect developers by terminating grants for any party who initiates a patent lawsuit regarding covered software 39 trademarks are the only form of ip not shared by free and open source software trademarks on foss function the same as any other trademark 40 a trademark is a design that identifies the distinct source of a product because they distinguish products the same designs can be used in different fields where there is no risk of confusing similar sources 41 to give up control of a trademark would result in the loss of that trademark therefore no open source license freely offers the use of a trademark 42 trademark restrictions can overlap copyrights and affect material otherwise freely available 43 the us supreme court described using trademark law to restrict public domain content as mutant copyright 44 in dastar corp v twentieth century fox film corp the court caution ed against misuse or over extension of trademark law without providing a firm decision on those mutant copyrights 45 46 trademark overlap can leave open source and free content projects vulnerable to a hostile takeover if outside parties file for trademarks on derivative works 47 notably andrey duskin applied for trademarks on the scp foundation a collaborative writing project when creating derivative works based on scp stories 48 permissive edit main article permissive software license permissive licenses generally originate in academic institutions like the massachusetts institute of technology permissive licenses also known as academic licenses 49 allow recipients to use modify and distribute software with no obligation to provide source code institutions created these licenses to distribute their creations to the public 49 permissive licenses are usually short often less than a page of text they impose few conditions most include disclaimers of warranty and obligations to credit authors a few include explicit provisions for patents trademarks and other forms of intellectual property 50 the university of california berkeley created the first open source license when they began distributing their berkeley software distribution bsd operating system the bsd license and its later variations permit modification and distribution of the covered software the licenses brought the concept of academic freedom of ideas to computing early academic software authors had shared code based on implied promises berkeley made these concepts explicit with clear disclaimers for liability and warranty along with conditions or clauses for redistribution the original had four clauses but subsequent versions have further reduced the restrictions as a result it is common to specify if the covered software uses a 2 clause or 3 clause version 51 52 the massachusetts institute of technology mit created an academic license based on the bsd original the mit license clarified the conditions by making them more explicit 53 for example the mit license describes the right to sublicense 54 one of the strengths of open source development is the continual process where developers can build on the derivative works of each other and combine their projects into collective works explicitly making covered code sublicensable provides a legal advantage when tracking the chain of authorship 53 the bsd and mit are template licenses that can be adapted to any project they are widely adapted and used by many foss projects 51 the apache license is more comprehensive and explicit the apache software foundation wrote it for their apache http server version 2 published in 2004 offers legal advantages over simple licenses and provides similar grants 55 while the bsd and mit licenses offer an implicit patent grant 56 the apache license includes a section on patents with an explicit grant from contributors 57 additionally it is one of the few permissive licenses with a patent retaliation clause 58 patent retaliation or patent suspension clauses take effect if a licensee initiates patent infringement litigation on covered code in that situation the patent grants are revoked these clauses protect against patent trolling 59 copyleft edit main article copyleft the copyleft sticker from an envelope don hopkins mailed to richard stallman in 1984 copyleft licenses require source code to be distributed with software and require the source code to be made available under a similar license 34 60 like the permissive licenses most copyleft licenses require attribution 61 most including the gpl disclaim implied warranties 62 copyleft uses the restrictions of ip law contrary to their usual purpose to mandate that the code remain open 63 the term and its related slogan all rights reversed had been previously used in a playful manner by the principia discordia and tiny basic the modern usage begins with richard stallman s efforts to create a free operating system in 1984 programmer don hopkins mailed a manual to stallman with a copyleft ⓛ sticker stallman who was working on the gnu operating system adopted the term 64 an early version of copyleft licensing was used for the 1985 release of gnu emacs 14 65 the term became associated with the fsf s later reciprocal licenses notably the gnu general public license gpl 66 traditional proprietary software licenses are written with the goal of increasing profit but stallman wrote the gpl to increase the body of available free software his reciprocal licenses offer the rights to use modify and distribute the work on the condition that people must release derivative works under a license offering these same freedoms software built on a copyleft base must come with the source code and the source code must be available under the same or a similar license this offers protection against proprietary software consuming code without giving back 67 68 richard stallman stated that the central idea of copyleft is to use copyright law but flip it over to serve the opposite of its usual purpose instead of a means of privatizing software copyright becomes a means of keeping software free 69 free software licenses are also open source software licenses 70 the separate terms free software and open source software reflect different values rather than a legal difference 71 both movements and their formal definitions require the covered work to be made available with source code and with permission for modification and redistribution 16 there are occasional edge cases where only one of the fsf or the osi accept a license but the popular free software licenses are open source including the gpl 72 mitchell baker drafted the mozilla public license while on netscape s legal team 73 practical benefits to copyleft licenses have attracted commercial developers corporations have used and written reciprocal licenses with a narrower scope than the gpl 74 for example netscape drafted their own copyleft terms after rejecting permissive licenses for the mozilla project 32 the gpl remains the most popular license of this type but there are other significant examples the fsf has crafted the lesser general public license lgpl...