[the_logos]

Free typically means, in common usage, that you don't have to directly pay (a MUD is still free just because you need to pay for a computer and internet connection to play it) for something with money or barter of chattel. The big exception there is that your personal time and energy is usually excluded as a cost. (So, spending time and energy on playing a MUD wouldn't typically be taken into account in the common usage of free.)

That's it really. If you can play for free, it's free, whether or not there is the opportunity to spend money. In fact, common usage has that even if the only way to get something in a game is to pay for it, it is still a free game as long as you don't have to pay for it to continue to play. For instance, if I'm giving away (legally-purchased of course) copies of Oblivion, I'm perfectly within my rights to claim that you can play Oblivion for free by accepting my free copy, even though there are things within Oblivion that are only obtainable by paying for them (downloadable content).

Note how standard this use of 'free' is.
* calls some of its servers free-to-play and some members servers. You can't even get onto the members servers (where the world is much, much larger) without paying a subscription. (Currently 182,000 players online).
* is promoted as free although becoming a member takes a one-time $15 payment. (18,000 players currently online.)
* Heck, just go to and click on the list of Free MMORPGs, most of which take some sort of payment to unlock things (unlike other games, like ours, that accept payment but in which you can always obtain anything without paying) but all of which are free to play.

--matt