That's sad news, but with the Unity license plans, it's understandable. I hope that you find time to come back to programming one day, and find another engine with a more friendly license. Personally, I use the QT framework, which is licensed under the LGPL (AFAIK; I never really cared because I never released my projects). Yes, this is not a game engine but only a GUI framework, but for things like DP it is enough. However, I don't know how good it mixes up with managed code, I always used it with C++.