...It doesn't depend on any external library and uses only a very small subset of POSIX APIs.
Despite the project name, you won't need your mouse at all!
A lot of embedded systems are free. We create a Lab and run some popular embedded systems on virtual system. You can port new system middle ware even if you do not have any hardware. eCos on Synthetic eCos on MINI2440 QEMU RTEMS on MINI2440 QEMU