Hi, David.

Adding to what Wayne says:

>>Here are my questions: Can I ethically charge them a fee for my source code, even though it was a >custom system I built for them?
>
>If in your contract, you specifically stated that you retained rights to the source, I don't see why not.

I would add that if it's not on a contract, or if there was no contract at all, then you SHOULD charge them for the source code.

>>If so, is there a standard method for determining what to charge for source code? I want to do the >right thing here.
>
>That's extremely difficult to do. Perhaps it is time to consult a lawyer and show the company that you are a serious individual. I would not go into this on my own!

You have to fix your price, but just for your information, I use to charge for the source code 300% the price of the executable product, and I do sign a contract in which the customer clearly states that the company will not resell nor transfer the source to any external party.

I value my source code and libraries very much, and even when I don't have any problem to share it with the development community, I make the companies that actually wish to get it pay well for it.

Hope this helps,