Did the email say you had to remove your 6.1 as well (still seems weird that they'd use email as a form of legal communication, but I digress)? There seem to be plenty of other people releasing 6.1 stuff, but Juicy and yours (more so than Juicy) involved 6.5 files. Good luck Indagroove, hope you can at least continue the 6.1 roms.
**Edit - Was the email from a guy named "James Young"? It seems like it's been established that he doesn't work for MS.
More info. here about it & real take-down notices