MediaPortal is open source.
I too am not an open source freak, it is really something important in (the geek part of) our planet, but sometimes (and again -unfortunately- MediaPortal comes to mind) it just SLOWS down things (yes slows down, not accelerates).
In MP since I gave it as example, at one time they decided to scrap the old buggy main menu setup mechanism (that DID have good functionality though) and start over. ONE YEAR LATER while the whole other project has moved greatly, I am still waiting for the ability to really configure the menus (the actual front end! what is more important in an HTPC?) at least as I did before they scrapped the old code. You'd say: Why don't you code it? (the "easy" but VERY offensive reply of the "common coder") Well I don't have the time and the last time I was involved in programming (it is how I started with computer btw), was maybe 15 years ago.
You see since such projects are build in the free time of most the programmers involved, sometimes you wait for parts of code for months.
Then if TOO many are involved, management and "fitting" of all those parts becomes an issue.
Linux is an example that worked well. I can give you many that didn't.
If directx was open source it wouldn't be directx 10.1, it would possibly be beta 0.1232.66 and you'd have to keep visiting a site to keep on top of updates. Ah and you'd never be with the "big players" (read: nVidia and AMD/ATI) that now actually MAKE their hardware to fit DX/D3D (just see how bad opengl is implemented in some of their products).
(To return to my previous post) To me having to choose a card (say a new hybrid card) not because it is the one I like, but because it has driver for the OS I want is a big limitation already. Also to look to the community to provide me with that driver (and not the actual company that MAKES the hardware), again is not too great in my mind.
Anyway. To each his own as you said.