Thank you so much for all of this! I admit, some of the legal wording I don't quite understand, but at least I know, now, that there is someone I can talk to for answers to specific licensing questions.

In fact, I have a couple of questions I would like to ask you now, if that's okay? And these questions might help others down the road. I've been looking for 'standard' limited use licenses for commissions, but I haven't really been able to find what I'm looking for. And the thought of having to write my own is.... daunting to say the least!

I have a commission I've been working on for over a year now. I want to include a limited use license for a map I'm making to a couple of authors who are writing a book. Now I agreed to do the commission free of charge, because I know these authors are doing this project on a shoe string budget. (As a fellow self published writer, I know how stressful that can be, especially on the wallet!), however... I also feel I should have the right to payment if this book really takes off... for example if it becomes mass produced by a third party (publishing company), or if it goes into mass reprint (different languages from that of the authors). Because this is 'pro bono' work initially, I'm retaining the copyright. So how would I go about writing a limited use license with that scope? I live in the state of NC, btw... I'm not sure where they live.

The second is on a commission I've just accepted. It will be a paid commission for private use (roleplaying campaign). Again, I will be retaining the copyright, and allowing client to use and distribute among his group for the sake of his game. He has initial creative input (there are certain things that have to be in certain places, and certain criteria has to be met ie: wall around the city, with 4 gates, etc) but he's leaving most of the creativity up to me. I have no problem allowing him to use the map I'm making for his group considering the amount he's paying me to make it. But if someone else approaches him to use the map I've made for his use (for what ever reason), I feel I should have the right to request the new person be directed back to me to purchase the right to use the map I've made. First, would this be considered reasonable, and second, how would I go about wording that? Follow up, since he will be paying me in installments, would it be reasonable to indicate that the product will be delivered once I'm paid in full?