I'd presume Krpano uses device fonts. As such, on your machine, any font installed there is usable in Krpano as well. However, any non-system fonts may not be available on someone else's system.

Unless you have complete control over the installed fonts on the machine that views the Krpano viewer, I would recommend sticking to system fonts only similar to the font restrictions in regular websites. That or find a way to embed your non-system font in a Flash file and use it like that, but that's a completely different scenario.