I don't know if there's anybody on here that uses linux for audio, (you kind of have to be a little bit crazy, and just enjoy doing things the super extra hard way to attempt it) In the line of doing things the hard way, I needed a drum machine (there's Hydrogen, but it's rather fixated on 4/4 time last time I checked), so, well, I made one. I released it under the terms of the GPL. So, in case anybody besides me was wanting a MIDI drum machine for linux that's sort of like Hydrogen, but with more flexible timing, one exists now.
Some rudimentary docs with a few (already slightly out of date) screenshots are here:
http://gneutronica.sourceforge.net
Download source code here:
http://sourceforge.net/projects/gneutronica/
If you want to hear a little bit of it, the first track on this thread has some simple stuff I did with it driving my Kurzweil (I'm no great drum track programmer, that's for sure.)
http://www.forums.myvirtualband.com/read.php?13,3425,page=1
(subsequent tracks on that thread have drums replaced by someone that knows better than I how to wield a drum machine.)
-- steve