hey guys. I randomly fell upon this today, and boy is it useful!
TuxGuitar
http://sourceforge.net/projects/tuxguitar/
theres only 2 things i can find wrong with it. 1, theres no stop/pause function, and 2 the font needs to be bolder.
I ran it on my dual g5 today (Its java) and had a blast with it. It behaves nicely, lets me tab out my riffs, edit midis etc etc
as a guitarist i know how important and widespread guitar pro is. Most of us would rather use Sibelius/Finale, but most bands/other musicians are on guitar pro (muchlike windows)
I figure if i mention it here, the 2 little problems i see could be cleared up quicker, plus more people will be happier now they can use Gpro files again.
Enjoy!