@Fwessels OpenHAB does currently not deal with assigning node IDs. I guess it is possible using the serial binding as I have seen described in another thread, but I don't think anyone has implemented it yet.
I have just finished porting one of the mqtt scripts to work with a serial connection as well as the existing socket interface, and am currently thinking of extending this (assuming that the author thinks it's a good idea) to assign node IDs. I think this should be relatively easy to implement, in which case that Perl script will be all you need between MySensors, a mqtt broker and openhab.
By the way, I'm running openhab on a five-year-year-old Intel platform running ubuntu server. It starts up in 10 to 15 seconds and is a more than powerful enough platform to handle every conceivable home automation need I can think of. And it was free since it was just lying around doing nothing. Okay, there is some noise and higher than necessary power consumption, but in a big house in Norway that is not a problem :-)