> I think I don't need to include MDL libraríes, I think just a link to them
> should be ok, so the library "uses" it directly from the source link.
Probably not, as you can only depend on something if it’s licensed Category A
or Category B in binary form even if it not in the release bundle. It may be OK
see the bit “For small amounts of source.. ”  for that it would be best to
ask on legal discuss.
IMO it would be best to contact them and get it clarified / ask to have it
relicensed as the first step.