Just saw that the source code for Vera has been released, that it is based on pluto, and that they are supporting and promoting heavily a UPnP based plugin system called Luup (offering upto $100k to developers contributing). Maybe this work could one day come back into LinuxMCE and then LinuxMCE could benefit from Luup plugin development?
The only part that is 'Open' is the OpwnWRT firmware, DCErouter and a few libraries...the DCE plugins they ship and the ZWave stack are locked down 100%...so I would not really see that as 'Open'. The plan for LinuxMCE is to make all of the codebase 100% GPL but even now the source to the PPL code is accessible and you can look it over and see how it works etc.
Andrew