Not really, you would have to completely rewrite the Orbiter which is much more than just a UI, and a huge piece of code.
LinuxMCE proper does not use ANY of KDE or Qt whatsoever.
The only exception is the Launch Manager.
I'm confused now: does the Orbiter use Qt? If not, what toolkit is the onscreen GUI built on? I thought all the old discussions of "UI3" were prioritizing Qt, because of some new Qt innovations (in KDE4). Maybe that was just because Aaron of Pluto was interested in cutting some deal with TrollTech (that I think never happened), and UI3 is still just an occasional discussion.
Not really, you would have to completely rewrite the Orbiter which is much more than just a UI, and a huge piece of code. Plus there are other pieces of LMCE unrelated to the UI that are covered by PPL. Why are you worried about PPL? It should only effect you if you intend to sell complete media/HA solutions bundled with hardware. Other than that, it has no effect on your usage of the system.
I'm generally interested in seeing any project come under a single license. I'd also like to see companies sponsor LinuxMCE which sell HW bundled with it, because they have the money and project management to move it along, market it to increase its popularity (which makes the community larger, which means more help and contributions).
I also think that the Orbiter code, which I've looked at (its messaging and network API, not its GUI), would be easier to upgrade if its UI were a discrete presentation layer, and not as integrated with the PPL code. The Pluto code remaining in LinuxMCE that I saw (in 0710) was written very badly, hard to trace or maintain.