Mumble uses Qt, the Cross-Platform Rich Client Development Framework. Qt is used for cross-platform GUI, network and database functions. Qt is both a widget toolkit and a set of very handy utility templates like container classes, network handling. It's all crossplatform, meaning that Murmur runs on pretty much any modern architecture, including the qmake files. I have a few projects that doesn't use Qt at all, but uses Qmake :)