Look my friend, unfortunately the authors of Serv-U do NOT use standard encryption routines. This would be dumb. They have written their own.

Brute force attack will NOT work in this case. Big reward or not, the only way I can see that this can be decrypted is to disassemble the actual program and ripping, for example, the encryption/decryption routine and using the program's OWN routines to decrypt the strings.