I think that most Linux distros will have GTK installed. No guarantee, but almost. KDE-based desktops, if I know well, use Qt instead, but surely some of the programs installed in the system must use GTK and upon installation, must have installed it as well as a dependency, so the odds are the binary will find GTK. On the other hand, if one were to compile it, my guess is that the development library would be missing, yet if the binary can run, that's enough.
Yes, that is the format. I have seen with the years that mostly the title and author's name end up being of any use. Other information is important only for the registry. In the tournament field, I usually specify what the track was made for, which championship, which race, etc. Maybe which car.