I'd say it's suitable for the kids. Obviously, it has some "Adult Concepts" but nothing I'm sure they haven't already heard all about in school.
It's a lot of fun and has some pretty good morale mesages hidden under the frocks and songs. You'll see Guy Pearce, Terrence Stamp and Hugo Weaving in a totally different way.
Back to the original topic, there's no problem with selling MP on eBay as long as it's not mis-represented. It may even help some people who haven't heard of it yet or can't download. If people are fooled into buying it they will soon learn that it's free, since any recent version has "FREE" in a big red star at the top. They can leave negative feedback if they don't think the sale was fair.
There was a news topic on this on the home page a few months ago, as it was happening a lot back then.