According to the project’s web site: HelenOS is a portable microkernel-based multiserver operating system designed and implemented from scratch.

The official GNU microkernel is still breathing – and now it's 64-bit Before Linux, GNU was working on its own Mach-based Unix compatible OS. Now, in the footsteps of Debian 13, there is a new release ...

"As the foundation for this new operating system, we chose seL4 as the microkernel because it puts security front and center; it is mathematically proven secure, with guaranteed confidentiality ...

Backed by the largest, independent team of microkernel developers, OK Labs open-source microkernel operating system, OKL4, offers the highest proven performance combined with strong protection and ...

It’s a Unix-like real-time, microkernel-based operating system that’s most widely used these days in automotive systems – more than 200 million cars run QNX-based software.

Jaluna-1 is a real-time component suite designed for carrier-grade projects requiring high performance and high availability. It is based on Sun Microsystems' Chorus microkernel operating system (OS).