Who knows what's in the contracts ... and what code moved around and survived where MSFT has no license to share code. Sure most of the things are out, but one helper function here, one there, maybe some data type they are still using relies on code from there ... it is a huge codebase grown in different ways over decades. And a few lines in an old subsystem and some and some successor of some original license holder can use it to refinance all their investments by sueing Microsoft.