- License compatibility
License compatibility refers to the problem with licenses of software packages which can contain contradictory requirements, rendering it impossible to combine
source codefrom such packages in order to create new software packages. [ [http://www.linuxdevices.com/articles/AT7188273245.html How GPLv3 tackles license proliferation ] ]
For example, if one license says "modified versions must mention the developers in any advertising materials", and another license says "modified versions cannot contain additional attribution requirements", then, if someone combined a software package which uses one license with a software package which uses the other, it would be impossible to distribute the combination because the two requirements cannot be simultaneously fulfilled. Thus, these two packages would be license-incompatible. [cite web
title=Stallman explains license compatibility while discussing GPLv3|]
Not all licenses approved by OSI or by the
Free Software Foundationare compatible with each other, thus not all the code under OSI or FSF approved licenses can be mixed. For example code under Mozilla Public Licensecan't be mixed with code under GNU General Public License(both licenses are OSI and FSF approved). The "FLOSS License Slide" shows if some common licenses are compatible [ [http://www.dwheeler.com/essays/floss-license-slide.html The Free-Libre / Open Source Software (FLOSS) License Slide ] ] .
Many of the most common free software licenses, such as the original MIT/X license, the
BSD license(in its current 3-clause form), and the LGPL, are "GPL-compatible". That is, their code can be combined with a program under the GPL without conflict (the new combination would have the GPL applied to the whole). However, some free/open source software licenses are not GPL-compatible. Many have strongly advocated that free/open source software developers use only GPL-compatible licenses, because doing otherwise makes it difficult to reuse software in larger wholes [ [http://www.dwheeler.com/essays/gpl-compatible.html Make Your Open Source Software GPL-Compatible. Or Else ] ] .
Also see the
list of FSF approved software licensesfor examples of compatible and incompatible licenses.
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