I am about to ruin your lives. Assuming this is news to you. You might know about it by now, being more into Who than I am.
There's a Doctor Who MMORPG.
It's browser based.
That means anyone can play it, Linux, Mac, or Windoze.
Doctor Who: Worlds In Time is released and maintained by Sega. The game is developed by Three Rings. I'm very familiar with Three Rings. They were one of the first of a new wave of game houses looking to make stuff truly cross platform. Their first effort, Puzzle Pirates, I have. It was Java based and worked on any major platform. They also did the wicked cool Bang! Howdy strategy game, same as Puzzle Pirates, completely crossplatform. Sega bought them last year, and this is their first effort under the banner.
The game is still in development, this is just the testing phase right now, but quite a bit is up. I would say they are almost release candidate. It's free to play, but I suspect freemium (free for regular users, but accessing better stuff means you pony up). But go. Answer the call. Here's the clicky again just in case.