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I feel a bit ignorant here, but are there open source license that simply can not co-exist? For example, could I write program Foo.c (using CDDL license), whic

I feel a bit ignorant here, but are there open source license that simply can not co-exist? For example, could I write program Foo.c (using CDDL license), which uses GPL'ed Bar.c and MIT'ed Dad.c (both unmodified)?

teacup50 11y ago
Most non-copyleft OSS licenses are compatible in some form, including with copyleft licenses such as the GPL; when used in a combined work, the combined work's license essentially reverts to the most restrictive of the licenses. In some cases, such as with WinObjC, reverting to the most restrictive license makes the work unsuited for its intended purpose. However, many copyleft OSS licenses have clauses that are genuinely incompatible with both other copyleft licenses, and less-liberal OSS licenses -- in such cases it's impossible to legally combine code under the licenses. In your example, the CDDL and the GPL have incompatible copyleft restrictions; your resulting program wouldn't be distributable under the provided licenses. A more common incompatibility example is that of the OpenSSL license and the GPL; GNU maintains a fairly complete list of incompatibile licenses here: http://www.gnu.org/licenses/license-list.en.html#GPLIncompatibleLicenses http://www.gnu.org/licenses/license-list.en.html#GPLIncompat...
dragonwriter 11y ago
> but are there open source license that simply can not co-exist? The GPL can basically not coexist with any other license, though lots of licenses (though perhaps fewer than the FSF claims, especially for GPLv2 and previous) allow code to be relicensed under the GPL (which is different from the code coexisting.) The reverse is emphatically not true, GPL code generally cannot be relicensed (downstream; the copyright owner can do whatever they want) to another license, except newer GPL versions if the optional "or any later version" clause is included with the GPL.
- mindcrime 11y ago
  My understanding is that the GPL can usually coexist with licenses that are non-copyleft, or with some copyleft licenses, as long as the license doesn't require the resulting work have any license restrictions beyond what the GPL requires. Anybody who's terribly interested in all of this will probably enjoy reading the GPL FAQ, especially this bit: http://www.gnu.org/licenses/gpl-faq.en.html#WhatIsCompatible http://www.gnu.org/licenses/gpl-faq.en.html#WhatIsCompatible IANAL, YMMV, HTH, WTFBBQ, ETC.
geofft 11y ago
Yes. It's not particularly different from writing program Foo.c (using CDDL license) which uses files Bar.c and Dad.c you took from your former employer without permission. There is no copyright license allowing such a thing to be redistributed. By default, all code is copyrighted and effectively proprietary. Open-source licenses are one way to grant permission to copy them. Fancy contracts with expensive lawyers are another way. You can only do what the licenses way you can do, and in particular, the GPL says that you may not apply "additional restrictions" and the CDDL has some clauses that the GPL doesn't. So there is no way to satisfy both licenses with regards to redistribution. You can negotiate for a different license. (This seems to be what MS did with objfw.)
0x0 11y ago
Yes, that's been a problem with at least ZFS on linux and a lot of apps linking to openssl earlier. Some would even claim that CDDL was designed solely to ensure ZFS could not be integrated with linux.

teacup50 11y ago

Most non-copyleft OSS licenses are compatible in some form, including with copyleft licenses such as the GPL; when used in a combined work, the combined work's license essentially reverts to the most restrictive of the licenses. In some cases, such as with WinObjC, reverting to the most restrictive license makes the work unsuited for its intended purpose. However, many copyleft OSS licenses have clauses that are genuinely incompatible with both other copyleft licenses, and less-liberal OSS licenses -- in such cases it's impossible to legally combine code under the licenses. In your example, the CDDL and the GPL have incompatible copyleft restrictions; your resulting program wouldn't be distributable under the provided licenses. A more common incompatibility example is that of the OpenSSL license and the GPL; GNU maintains a fairly complete list of incompatibile licenses here: http://www.gnu.org/licenses/license-list.en.html#GPLIncompatibleLicenses http://www.gnu.org/licenses/license-list.en.html#GPLIncompat...

dragonwriter 11y ago

> but are there open source license that simply can not co-exist? The GPL can basically not coexist with any other license, though lots of licenses (though perhaps fewer than the FSF claims, especially for GPLv2 and previous) allow code to be relicensed under the GPL (which is different from the code coexisting.) The reverse is emphatically not true, GPL code generally cannot be relicensed (downstream; the copyright owner can do whatever they want) to another license, except newer GPL versions if the optional "or any later version" clause is included with the GPL.

mindcrime 11y ago
My understanding is that the GPL can usually coexist with licenses that are non-copyleft, or with some copyleft licenses, as long as the license doesn't require the resulting work have any license restrictions beyond what the GPL requires. Anybody who's terribly interested in all of this will probably enjoy reading the GPL FAQ, especially this bit: http://www.gnu.org/licenses/gpl-faq.en.html#WhatIsCompatible http://www.gnu.org/licenses/gpl-faq.en.html#WhatIsCompatible IANAL, YMMV, HTH, WTFBBQ, ETC.

geofft 11y ago

Yes. It's not particularly different from writing program Foo.c (using CDDL license) which uses files Bar.c and Dad.c you took from your former employer without permission. There is no copyright license allowing such a thing to be redistributed. By default, all code is copyrighted and effectively proprietary. Open-source licenses are one way to grant permission to copy them. Fancy contracts with expensive lawyers are another way. You can only do what the licenses way you can do, and in particular, the GPL says that you may not apply "additional restrictions" and the CDDL has some clauses that the GPL doesn't. So there is no way to satisfy both licenses with regards to redistribution. You can negotiate for a different license. (This seems to be what MS did with objfw.)

0x0 11y ago

Yes, that's been a problem with at least ZFS on linux and a lot of apps linking to openssl earlier. Some would even claim that CDDL was designed solely to ensure ZFS could not be integrated with linux.