There seems to be a new way of doing PC keyboard as piano that at least two programs are now doing, with 2 1/2 octaves, and the black keys are diagonally positioned like on a real piano (see LMMS wiki under Piano Roll). This also requires use of the number key row since two rows are used for each octave. I couldn't find any info on remapping the "keyboard as piano" keys for OpenMPT. Please post how to edit the config file, or give me a hint where to start looking in the sourcecode, to provide remapping 1-0 and A-Z all to musical note entry.
If you load in another keypreset file, you can accomplish this right in OpenMPT. The traditional keypreset file is doing it differently, but many of the keypreset files that you can download and find in the RC packages have this kind of layout.
There are keypreset files based on programs like FT2 and IT that do this too. And these two programs are not the only one. Almost all tracker based software does it this way.
Open the Options window and go to the Keyboard tab. Set the note keys as you like them, done. Also, this is not new but has been the default key style in many trackers like FT2 and IT, and there are various keymaps in the "ExtraKeymaps" folder which are modeled after those trackers.