From the designer perspective there are tons of alternatives to arial - like Nimbus Sans L or Deja Vu.
I am not sure about the linked FAQ above...there are some usecases it might be like that and it could be okay. But in my opinion there are to many open questions. I mean you couldn't sell a book, any movie cover or print a flyer with arial on it. I can't give you a clear answer on that. I would definitly prefer a font who's license clearly allow you to use it.
We are talking about realy small differences on high res-displays. On embedded-devices a low pixeldensity they are even smaller. So if you are using a font like Joel said you are on the safe side and it doesn't realy effect your endproduct
