Compatibility of Liberal Licenses

Compatibility with other licenses

If you are going to combine a material which is licensed under a Liberal License with another material licensed under a license other than a Liberal License to a larger work, then the compatibility will depend on that other license.

See also examples of license combinations in larger works.

Some licenses are reciprocal. Reciprocal licenses are also known as "share-alike", "copylefted" or "viral" licenses. The terms "copleft" and "viral" are more common for open source licenses. For the purposes of the Liberal Licenses the term "reciprocal" is used. What means "reciprocal"? In short: a reciprocal license requires derivatives of the licensed material to be licensed under the same license or at least a license that grants the same rights. A reciprocal license may also define a list of compatible licenses. A strictly reciprocal (aka strong copyleft) license usually requires also that a larger work containing or linking to the licensed material is licensed under the same or an equivalent license.

Liberal Licenses are reciprocal as well, just in the sense that derivatives of the licensed material must be licensed under the same license. The main motivation behind the reciprocity is to prevent that the licensing of a material with a specific set of granted rights, restrictions and conditions could be replaced for an altered version of that material by a different licensing which takes away too many rights or vice versa takes away the protection of the intellectual property of the original licensor. While for copylefted open source licenses it is only about protecting the granted rights of the licensees, for the Liberal Licenses the reciprocity is not onesided and thus also about the rights of the licensor.

The LL-AS-RR is relenting reciprocal, but all other Liberal Licenses are more or less strictly reciprocal. The LL-AS-RR relents, means it waives its reciprocity, where a compatibility would not be given otherwise - and therefore provides a great compatibility with other reciprocal licenses. The other Liberal Licenses which are more or less strictly reciprocal are still compatible with many other licenses, but not with strictly reciprocal ones.

Therefore, for the very best compatibility possible you may choose the LL-AS-RR, but be aware that the downside of the enhanced compatibility, due to its relenting nature, is the possibility that the licensed material (in a larger work) will be licensed with a license that creates a loop hole for a licensing with an unwanted set of rights, restrictions and conditions. To be safe against these loop holes, you should use one of the other Liberal Licenses unless you think you need the compatibility with other reciprocal licenses for your material.

Please find examples of license combinations in larger works in the table below (the green cells show the possible licenses for the respective combination).

1) compatible as "combined works" under specific circumstances, e.g. the "upper limits for the commercial usage" must declare no limitations
2) compatible as "combined libraries" only
3) classical proprietary licenses which grant lesser rights to the licensee than Liberal Licenses