LiteBSD is a variant of 4.4BSD operating system adapted for microcontrollers. Currently, only the Microchip PIC32MZ family is supported as a target. It is equipped with MMU with paging support, and 512kbytes of on-chip RAM. These resources are enough to build a compact networked embedded system.
For more information, see LiteBSD Wiki pages.
Precompiled binaries for several PIC32MZ boards are available from Autobuild Download page.