Esenthel Engine, a next-gen game engine supporting Windows, Mac, Linux, Android, iOS and Web, 14 years in development, with hundreds of customers world-wide is now going open source with brand new licensing options.
I don't see any "edit" button, so, I wanted to clarify my previous post, the engine now has brand new full source code license option, that's now very approachable, but still paid. I don't mean to imply that it's available for free. Thanks!
I think a common term for that is "shared source" - i.e. shared among licensees, but not open for all to see.