Contributions are welcome, but please contact me and work with me up front. At the time of writing this note, the entire code base is developed by me (Curt Olson) and I have a large emotional investment in it. I will be cautious and skeptical if someone drops a big pull request out of the blue.
I understand I can't do everything alone, and I'm not the only person with good ideas. So if you have an idea of something you'd like to add or contribute, please talk to me up front. Let me help you work it into the code base, and please help me get to know and trust you.
I ask that all contributions be GPLv3 compatible.
I further require that ownership/copyright of any contributions be assigned to Curtis L. Olson. The intent of this requirement is so that later if I would like to update the license to something more free or flexible, or make some larger decision about the project, I don't have to chase down a myriad of contributors to try to achieve 100% consensus.
I have been involved in open-source projects since the early 90's. I am one of the founder of the FlightGear open-source flight sim. All the code I develop for my day job (U of MN AEM UAV lab) is licensed under the MIT open-source license. So please understand that I have a long history with valuing open-source and open-source contributions.