If I make a website for a client and all the coding is original work and I sell them a non-exclusive license to use the material in their business, would they be allowed to modify the source code in the future, or even have another developer come in and modify it for them, or is this only something they can do if they pay extra for the exclusive license?
Disclaimer: I am not a lawyer or a legal professional, and this not meant as professional legal advice.
From the Digital Media Law Project:
"A license is a grant of permission to exercise your rights under copyright...
- When you give someone a non-exclusive license, you give the licensee permission to exercise the right in question, but you also reserve the right to continue exercising it yourself and to authorize others to do so.
- When you give someone an exclusive license, you promise that the licensee and only the licensee may exercise the right. This means that when you grant an exclusive license, even you may not exercise the granted right, nor may you authorize anyone else to do so.
So a license means you retain ownership of copyright even though another party is now authorized to act as the owner of the copyright.
An exclusive licensing agreement differs from a non-exclusive one in that it limits you -- the orginal copyright owner of the work -- from licensing the work to anyone else. Presumably you would charge a hefty premium for this legal guarantee to the client that they are the only party with the legal right to use the work -- even you have given up the right to use the work for the duration of the agreement, though you do retain ownership of the copyright throughout.
Whether exclusive or non-exclusive, licensing your work to the client without restriction means they have permission to use it as they see fit, including modifying it, bringing in another developer to build on it, etc.
You may however limit rights licensed in an agreement. As an example, when I deliver a web site design to a client do so under a limited license. The client is granted the right to use the design work for only one business -- the one I was contracted to design for. They are not permitted to copy/paste the design with altered content to market another business.
Conversely, the client may negotiate a limited exclusive license with my firm -- for instance that I will not sell the same or similar design to a competitor within their market and region. Again, this is something for which I would charge a premium. The client is paying for a competitive advantage.
Regarding the specifics of your question, as stated in Section 106 of the Copyright Act you can limit
"The right to make derivative works based upon the copyrighted work (this basically means the right to make adaptations of the work)"
in your copyright agreement. However you should be up front and make sure the client knows and understands this before signing documents.
Also ask yourself why you feel this is necessary for you, and how this serves the best interests of your clients. There are other avenues you can pursue that will lead to repeat business for yourself and a better end result for your clients.
It all depends on your contractor. You should never rely on things that are "generally known" or you may be negatively surprised.
So if the contract is still active, I suggest you clear this explicitly in the contract.
If you however want to know how some of us deal with this, I personally hand over all the sources and do not care if anyone else will modify the code or not. If someone modified the code, screwed things up and the client comes back to me asking to fix this, I will rarely fix messed code but I will continue from my own code and charge him accordingly.
If you make a website for the client, the CLIENT owns the work product (it is a work-for-hire). You can't license something to the client that the client already owns!!!! If your contract doesn't specify that you retain ownership of work product, then YOU DON'T OWN IT.
Accordingly, the client can put another developer in the mix for modifications at the client's discretion. Once you hand it off, you are not responsible for it -- not EVER. You might have a client who badgers you to do minor fixes, or even repairs after someone else screws things up -- don't do it for free!