I'm no legal expert, but it's something to do with the fact that the original code for this was not open source, and was written by a dev not associated with either project. Some Graphene dev updated it for android 12, under whatever license, which somehow meant they could tell calyx they couldn't use the code for android 12. I seem to remember reading somewhere that Graphene are rewriting the code under a full OS license, which they said they would have no issue with calyx using that under the rules of that license.