Personally I do not think this will work. If this would be a legitimate company, then they would have nothing to hide.
Secondly, I BET (haha) that they want to receive the funds first, before releasing the code. To many people try to make money like this.
Or even when they provide you a document, it will be a useless software script, and then you lost your money.
OP: Maybe it is an idea to put in your announcement that you are open to provide scripts, before people have to transfer the Bitcoins to you. That would help a lot, for sure.
And regarding the demo, do you provide an back-end and front-end?

ya.ya.yo!