I just took a look.
I needed the following files in the diablo home directory:
* devilutionx.mpq
* DIABDAT.MPQ
devilutionx (the application) and diablo.ini were already installed by original download, so in total there were 4 files. I also have MANUAL.PDF but I doubt that matters.
Even so, it was too slow to play for some reason. Maybe I need to tweak settings in diablo.ini. Not sure. I am running on SAM460cr.