Very little to add other than yes, you can still register it, as of at least a year ago (when I registered another copy). I dont recall if Mensys (or BMT - forget who I ordered from) provided the key or the author did.
Perhaps contacting one of them (Mensys/BMT) regarding contacting the author might work.
-Rob
It would seem to me that if someone could get their hands on the sources to X-File, that would be a good place to start.
Upgrade that and modernize its look and feel, eliminate the remaining bugs and save oneself from having to re-make the wheel.
I do not know if the author is still in the OS/2 community, but the program itself hasn't been updated in a long time which is a clue.
His name is Michael Shilllingford of Codesmith Software from Canada and as far as I know you can still register the software with BMT Micro.
Maybe someone in the community has something to add that could help.
UPDATE 01: Both Mensys and BMT Micro still sell x-File.
UPDATE 02: I ordered through Mensys, and received my invoice via Mensys, but my product key (with Mensys cc'd) from BMT Micro. Thus, I'd suggest contacting BMT about a method to contact the author since they seem to be the ones dealing with registration for this product regardless of which of the two places it is ordered from.