ActorX Importer for 3ds Max does not supoort importing of multiple *.psa files.
The modified maxscripts under the 'mod' directory supports importing of multiple *.pas files which are exist in the same folder and exporting all loaded animation files.
Maxscript files under the *'maxscript' directory are just to keep tracking of the original script files which means that are same as the script files found on the ActorX Importer for 3ds Max page.