FYI TuxGuitar is a FOSS player that can load/play/edit PowerTab and GuitarPro files. Multiplatform too. It's not completely 100% bug-free, but it's good enough to load and play most tabs flawlessly.

Or for a more robust piece of software (especially if you do tabbing/composing yourself or you want to generate/edit a tab from a MIDI file), MuseScore is also FOSS and can import GuitarPro files no problem. With its recent UI overhauls it's really become top-notch IMO.