We just ported an old Java PDP-11 emulator that runs the 1975 version of Bell Labs Unix onto the plug!
It works like a charm - even though it is being interpreted 2 levels deep - PDP-11 intructions emulated in Java which is running a VM on the ARM!
We used the OpenJDK -cacao VM, and it is fast enough. We emulated the DH-11 serial multiplexor with Telnet, so a bunch of users can telnet into the plug as if they dialed in on modems!
We used the original Unix Disks from the Unix Preservations society - and have it running from the SD card.
It is a H*ll of a lot smaller than the original PDP 11/70 that used to run this software....