DES_GEN was written as a POC for a specific application that shall remain anonymous several months ago.
The belief at the company was that cracking DES requires custom hardware (See EFF's US$250,000 DES cracking machine) so the vendor refused to update to newer methods of password storage.
Here's a single threaded x86 based slap in the face for that company written in perl none the less - yes a dictionary file and some fairly weak mutations cracked your root password in 46 minutes.
I'm not sure if anyone will get any use out of this, but here it is.
--If there is enough interest in updates or future releases Threading and CUDA support may be added. Cheers.
Perl, Word list, DES