The seL4 Microkit is an operating system framework on top of seL4. It provides a small set of simple abstractions that ease the design and implementation of statically structured systems on seL4, leveraging the kernel’s benefits of security and performance.
The Microkit is distributed as an SDK that integrates with the build system of your choice, significantly reducing the barrier to entry for new users of seL4.
The seL4 Microkit is part of the repositories managed by the seL4 Foundation. It is currently mainly maintained and developed by the Trustworthy Systems research group at UNSW. See also the Microkit project page there.