I'd recommend that you charge about a lot more money for the firmware source code.

I think someone in the states would easily consider paying $150 to $250 for some real, documented source code for a business application. Even $100 would be reasonably attractive for a hobbyist project.
The only thing countering a buying decision would be the risk that the firmware purchased would be easily usable to that customer.

By the way, I think its a great idea to sell firmware packages to potential US customers. The differentials in value of money from the US to many other nations makes it a wise market if you can connect with the customers.

I'd recommend advertising in the US Hobbyist Magazines to see if you can find your potential customers. Here, most of us do this for a living and if we purchased it, we'd be spending company money... that means the price could rise but you'd have to do more to convince the company customer that it is really useful before they buy.

And then you have issues about protecting your delivered source code from customers copying it for friends. Hobbyists tend to do that, less so companies.

If this topic is deemed inappropriate for 8052, I'd be glad to chat about this on an IRC or via email.

duh-money