I was wondering if anybody had heard of a library, preferably a .NET assembly, but Java will do as wel, that allows you to read the data in a Guitar Pro file (.gp3-gp4-gp5)
Please look through my open source project that is written in C# for Windows Phone7:
http://phoneguitartab.codeplex.com/
This is tablature viewer for Windows Phone 7. It can open guitar pro (.gp3, .gp4, .gp5) and text based files (I've used open source projects in Java to create guitar pro parser in .NET). Unfortunately it isn't finish yet but I hope you find something useful in this project.
Update: GuitarPro functionality was moved into branch