Before building mensis you must build fontforge (or at least install its libraries). Then in the top level 'fontforge' directory do the following:
$ tar xfj mensis_full*.tar.bz2 $ cd mensis*/. $ ./configure $ make $ su # make install
If you want to use Mensis's grid-fitting debugging capabilities you must install FreeType's library. You must also either live in a country where Apple's TrueType grid fitting patents are not applicable or have obtained a license from Apple allowing you to use their patent and then compile the FreeType library with grid-fitting enabled (in ftoption.h), then set similar #defines in config.h. For more information contact Apple's legal department or see FreeType's patent page.
If you have freetype configured properly then configure should be able to choose a configuration that is appropriate.
Mensis isn't very far along. I may not pay much attention to bug reports for a bit, but I'm sure you'll find some. If you can isolate one and come up with a reproduceable minimal case, that would be great. The executable has symbols in it so if you run it in gdb you should be able to get a stack trace... Do what you can.
You may subscribe to it on sourceforge: http://sourceforge.net/mail/?group_id=84696
This program would have been far harder to write if the freetype library hadn't done almost exactly what I wanted.
Valek Filippov gave me the russian translation.