With so many free games out there it's pretty hard to find one that has the right balance of content and at the same time doesn't try to get your money and chance it gets. Of the many games I've seen, Adventure Quest does pretty well.
Story and Messages - A generally light hearted romp through a fantasy world. You are placed on the "good side" so to speak when you begin and fight for justice, peace, and everything in between. There are occasional "Alignment Choices" in some quests which lean towards one of the elements of morality (Good, Evil, Chaos, and Unity). Often, these simply change the outcome of the quest and in most cases you can go through again and make a different choice. There are quite a few characters within the game with some good, some evil, and some morally gray. Though the game is not bursting at the seams with great role models, there are many morally good characters and those that act in the interest of others. The game is mostly fighting sections in a turn-based RPG format. The use of weapons such as swords, bows, etc. as well as magic is shown, but no bloodshed.
Language - There isn't really anything in the language department that isn't to be feared. There is no swearing of any type, the most you'll get is a heck or dang. A large slice of the comedy in the game comes from puns, most of which are either family friendly. Occasionally, these jokes do make a nod to things that could be considered "more adult" but any teen or pre-teen will be fine with them. (The most I ever saw was a female character who commented on the character carrying around many items with the joke "You should have worse back problems then most of my girls here.")
Drinking/Drugs/Etc. - There is no mention of any such things by name. There is occasional mention of a fictional juice named "Mogleberry Juice" but it is not implied to be alcoholic.
Purchases/Microtransactions - Adventure Quest has only two things to purchase. The first is a membership referred to "Guardianship" and is a one-time payment of 19.95USD (per character). Guardians can also upgrade to "X-Guardians" for 5USD more when purchasing standard Guardianship or later on for 9.95USD. Buying Guardianship unlocks all of the content the game has to offer. Previously I mentioned the cost is per character, but note that you can change your characters name, gender, and appearance without having to pay additional fees. The second paid product is Z-Tokens, a secondary currency in game used to buy some powerful items. However, in most cases, Z-Token items can be purchased using gold but at a later level. Z-Tokens can occasionally be found in-game after defeating monsters. The prices for Z-Tokens vary by the amount you are purchasing. The prices can be found at: https://secure.battleon.com/aq-buytokens1.asp
Safety and Privacy - There is no interaction with other players in-game and your credit card information is not saved to your account after a purchase. All purchases are encrypted through SSL.
Additional Notes - Players can connect their Adventure Quest account to a "Artix Master Account" which is used to play other games by the studio and make purchases for their account with "Artix Points" that can be spent in any of their games. However, getting a Master Account is only required for some of their games and Adventure Quest is not one of them.
For information on what you can do after linking to the Master Account: https://portal.battleon.com/store/packages/adventurequest.asp
Master Account "For Parents" page:
Overall - Adventure Quest is a relatively non-violent free RPG for teens and pre-teens. Adventure Quest has few microtransactions and lots of content. Adventure Quest has relatively good messages but also has moral choices.