The usual solution in the business I am in is to get them to sign an NDA - a non disclosure agreement. That prevents them from disclosing and disseminating your property which is the IP (intellectual property) which is the source files. On the other hand I usually don't care a jot and just give them the whole kaboodle. But then most of what I do involves tools I have written so its of limited use to them anyway. But when writing code I don't do open source and keep all source files well locked up. I have been requested the source files numerous times for ViewingDale even to the point of trying to do bug hunting for some guys problem which I could not replicate until I worked out he was using a different OS and was trying to port the damn thing over. So yeah, if you care about it and have reservations about it then don't. Your not under obligation to supply more than was agreed.
Which brings up a secondary point, be careful about what you are agreeing to supply at the outset. Make sure your contract target is well defined and ensure that they agree to the final before billing them the final amount for the work. Any extras after that point are at your discretion - you have fulfilled your contractual obligation.
I think people should consider these issues before setting a price too. Sometimes they set the price for the work to do in making the image but there is more involved in making your customer happy and satisfied that he has the required legal protection for the work. That, for some awkward customers, can be more effort than the making of the map. You can usually spot these people from the request they initially submit. The more legally / commercially unrealistic it is the more you want to walk from it. People who have clear and realistic expectations about what they are getting and what they are not are the best to work for. Those are the people who you stick with and are usually the people that get projects completed and are generally successful.
EDIT - Ohh this just popped up on the radar so thought id share:
http://www.softwarebyrob.com/2010/12...oxic-customer/
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