If code components that were licensed under different license conditions are compiled to form a new work, a question arises: Is the common use of the code permissible under license law? If for example code A under license X is linked with code B under license Y to form a new program, licenses X and Y must permit this. If this is the case, license compatibility exists.
License compatibility is particularly important for copyleft licenses (→ What types of licenses are there for open-source software, and how do they differ?) since licenses such as the GPL provide that derived works may only be used under the same license conditions (that is, those of the GPL). Hence copyleft licenses are only compatible with other open source licenses when one of the following conditions is met: Read More...