Bluebottle is a powerful operating system developed in the Programming Languages and Runtime Systems Research Group, based on the Active Object System (Aos) kernel. The Aos kernel provides a compact runtime environment for the Active Oberon language (pdf)

oL4 is a small OS containing the Io programing language on top of the L4 microkernel. It runs the IoVM as a single server in kernel level, allowing direct hardware access and independence from having a full blown operating system and userland.