Bungo,
This question may belong in another forum since it's not a direct discussion of the books themselves. But, if that is so, Esty or Legolas will move it to where it belongs...
In the United States, and I believe in Great Britain, the books are still protected by copyright law. All the profits go to the Tolkien estate, and they have the right to bring someone to court if they feel someone has overstepped that bounds.
In recent years, the Estate has been fairly active in asserting those rights. For example, not too long ago a number of map websites had to shut down or delete their map collections because the Estate lawyers threatened to bring a suit as an infringement of copyright. I have no doubt that the Estate would react similarly if someone tried to get one of our fanfictions or RPGs "published".
Yet, at the same same, I can tell you that there have been some spin-offs published outside of the United States. I've heard of such stories published in book form in Russia. Apparently, Russia and certain other countries have never signed on to the Bern Convention that is the basis of international copyright law, so there are "holes" in enforcement.
And I wonder about the old ICE publications that were published in this country. These were RPG guides that you can still get through something like e-bay which included stories using Tolkien-like characters in a world something like Middle-earth.
Perhaps someone knows more about these exceptions.
You might want to look at this older thread:
rip offs
Also here on
Merp and ice. and
here on Merp.
Perhaps most interesting of all is Mhoram's old thread discussing the
expiration of copyright.
It sounds from what Mithadan said that the Hobbit may enter public domain in the next five years. It will be interesting to see what happens then.
Having said all this, I am definitely no attorney

, and that is who you'd have to go to for a definite answer on copyright issues.