Compatibility of Liberal Licenses
Compatibility with each other and with other licenses
The compatibility of a license with other licenses is important for licensed materials which might be combined with other materials licensed under a different license and the compatibility is even crucial for works which are meant to be combined with other materials such as software libraries.
In general the Liberal Licenses provide a great compatibility, but in detail the compatibility depends on the license choosen. What means compatibility in terms of licensing? You might wish to alter a licensed material, but maybe you want to use a different license for the altered material. You might wish to combine a licensed material with other materials licensed under a different license to a larger work or you simply add it to a collection. Liberal Licenses differ between these cases, even if in practice the difference is often not so clear. Moreover, the assessment if a licensed material became a part of a larger work or a bare collection or is just an altered material, depends on the respective governing copyright laws and possibly on judgments.
As a rule of thumb: If you just link from your own work to a licensed material or you just add materials which can be considered reasonably as self-contained, reusable components to a licensed material, then the result is a larger work (that consists of different components), for instance a software using libraries, but otherwise if the added materials are not self-contained, not reusable or too tightly coupled with the licensed material (or the licensed material is altered in another manner e.g. parts are removed) then the result is not considered as a larger work, but simply as altered or changed material, for instance a novel where a new chapter is added - or maybe just a missing dot is added. Imagine a licensed material is a photo, you edit that photo and add it with other photos (possibly under other licenses) to a collage. Then you have an altered licensed material (the edited photo) within a larger work (the collage). If you just add a licensed material to a collection where the collected elements exist side by side but with no connection to each other and no coherence or common context, then that collection is not considered as a larger work. For instance if a licensed photo is added to a bare photo collection on a website, then that website is not a larger work if it just serves as the technical medium to provide that collection.