The central place for all the documentation related to Qtpfsgui is on this sourceforge wiki.
Thomas Martin has provided a German translation of Qtpfsgui's manual. Thomas Martin's website (in German) dedicated to Qtpfsgui can be found here.
If you want to contribute translating Qtpfsgui for your language here's an howto that explains the procedure to become a maintainer.
See also this tutorial (french), that covers version 1.7.1.