Xenko 3.0 has been released with the very permissive MIT license. Silicon Studio is no longer supporting Xenko.
This is Good News and Bad News. Good news in that a powerful engine is now easily accessible to all; Bad News in that the Game Engine competition can be considered too stiff to allow new contenders to thrive. I'm inclined to think that poor adoption meant poor financial viability which led to Silicon Studio letting go of Xenko.