Companies also don’t just die just once, they can do so repeatedly. Xapian is an example I like to quote here. It started out as a GPL v2+ licensed search project called Muscat which was built at Cambridge. After several commercial acquisitions and transitions, the project eventually became closed source (which was possible because the creators held the copyright). Some of the original creators together with the community forked the last GPLv2 version into a project that eventually became known as Xapian.

What’s the catch? The catch is that the only people who could license it more liberally than GPLv2 are long gone from the project. Xapian refers to its current license “a historical accident”. The license choice causes some challenges specifically to how Xapian is embedded. There are three remaining entities that would need to agree to the relicensing. From my understanding none of those entities commercially use Xapian’s original code today but also have no interest in actually supporting a potential relicensing.

Unlike trademark law which has a concept of abandonment, the copyright situation is stricter. It would take two lifetimes for Xapian to enter the public domain and at that point it will be probably be mostly for archival purposes.