Latest stable in gentoo is 0.6.3. This requests supports bug #19454 (ebuild addition - pingus 0.6.0 ), whose documentation really asks for 0.6.5.
Tried to compile 0.6.5 - had a problem: Compiling Sources/GL/GLX/displaycard_glx.cpp Sources/GL/GLX/displaycard_glx.cpp: In member function `virtual void (* CL_GLX_DisplayCard::get_proc_address(const std::string&))()': Sources/GL/GLX/displaycard_glx.cpp:366: `glXGetProcAddressARB' undeclared (first use this function)
I think I solved it.