I just emailed Tonehammer about their Anti-Drum II saying it'd be great to get it in GURU format.
http://www.tonehammer.com/?p=1770 They said it may happen if enough people showed interest. With the dirth of cool drum libraries for GURU (Goldbaby and Bitword aside) it'd be great for more stuff like this to become available.
If anyone else would care to drop them a line here http://www.tonehammer.com/?page_id=1280 maybe we could make it happen.
The problem I see for 3rd-party Guru libraries is the mapping. Will they be set up as 4x each of Kick/Snare/etc like the pre-labelled pads, or will they have some other mapping, which would likely be more flexible but non-standardized?
Along those lines, I'd be curious how most Guru users map their own custom kits. I've never used the "four each" approach personally. And how does this all translate to Guru's midi grooves?