GC greatcode is a C/C++ source code beautifier that is now fully open source.
The distribution zip file contains the source code together with a windows executable. Executable files for Linux can be build from the source files (makefiles being constructed via premake4).
The original author of GC no longer has time to maintain the source code, but others are adding to the code base. If you are interested in adding to the code base, contact one of the administrators who will add you as a developer.
gcgreatcode works perfectly.
Nice and simple.