Last year Stockfish attempted to enforce the GPLv3 version of the clause against ChessBase. I'm not sure how it has turned out so far.

https://stockfishchess.org/blog/2021/our-lawsuit-against-che...

Previous discussion:

https://news.ycombinator.com/item?id=27896386

The slides I attached are from a talk which mentioned one example. I remember seeing some version of this talk at some FOSDEM, likely https://archive.fosdem.org/2015/schedule/event/samba/