(Gammas are squeezed together and \bf is ineffective, which is not so
with modern).
The characters are squeezed together because the font has wrong metrics.
If the assumption that "mdugmr7m.tfm" contains the metrics for
"md-gmm7m.pfb" is correct, then fontforge show it (mdugmr7m), contains
bold characters, which then should show.
When you use a Type 1 math font with ConTeXt MkIV all characters in the different
files are mapped to the corresponding unicode points but these mappings aren’t
complete (e.g. bold uppercase greek letters aren’t mapped).
For some fonts you would also need a custom mapping because not all fonts
put the symbols in the same position.
Wolfgang