Here is a first version of the GMP/GTP bridge:
http://hera.mni.fh-giessen.de/~hg53/gmp2gtp-0.1.tar.gz
I was able to let GNU Go 3.3.22 successfully play against both programs from the Gifu contest website: cgftest/CGFGO.EXE -- a graphical Go front-end cgfgnu02/Cgfgnugo.exe -- a very old version of GNU Go Both colors worked well.
Not yet implemented are 'undo' and all sorts of time settings. The full GMP variant has not been tested.
Paul, thanks for your gmp patch - this was very much along the lines I had already thought of myself.
Gunnar, the options now begin with double dashes. Please let me know if there are other style guidelines which should be followed.
Questions and bug reports are welcome.
Hellwig