There where talks about bringing XBL to Xbox again, most of the discussion happened at Assembler games.
https://assemblergames.com/threads/open-source-xbox-live.44462/ there you go. Assembler forums are dead tho.
And unfortunately, it seems as though that project is, too. After reading the specifics of it on that thread, it really seems like too big of an undertaking for anybody but MS themselves to do.