I've never used it so can't speak from any experience, and unfortunately it doesn't seem particularly active (and doesn't mention a current status anywhere), and doesn't have a license, so shrug. When it's been posted here (https://news.ycombinator.com/item?id=40211891), people seemed pretty excited about it.
Specifically, "Users may link this kernel with closed-source binary drivers, including static libraries, for personal, internal, or evaluation use without being required to disclose the source code of the proprietary driver.".