Announced a few days on their official blog:
You read that right. Xenko 3.0 is out now, released under the permissive MIT license.
From now on, you can use and modify Xenko completely free — whether you’re a professional, a student, or just looking for a new hobby. This includes both the runtime and editor.
Main focus for this release was on the open-source transition, but Xenko 3.0 also includes some new features, such as a switch to the new C# project system, video, hair and skin rendering.
What's interesting, is that Silicon Studio are no longer going to be supporting it. This means that it's now down to the Xenko team to work on it independently along with the community. To be clear though, if you do plan to contribute they have a Contribution License Agreement they require you to sign.
As I understand it, they previously had a dual-license with the code under the GPL, but for those who that caused issues they also had a paid-for version. With it now being under the MIT license, it should remove any barrier for people to use it. Linux support, from what I've read is currently experimental. They also said on Twitter that the Linux build is currently disabled, but it should be enabled again soon.
It seems like a pretty advanced game engine, with support for both OpenGL and Vulkan. Nice to see it so open now, will be interesting to follow it along.