Decoding a file

I've bought a script from Sibsoft - xfilemirror and [login to view URL] is encrypted. I would like to decode it and I'm looking for someone who can tell me how can I do that. I'm seeking knowledge. I'm sure there were already similar requests so I hope that person who already solved this would contact me. I can provide you with root access to my vps server so you can show me what needs to be done and how. Thanks