On the other hand clones of Tetris are being shut down because they use the same mechanics in their games.

No it wasn't. Read the judge's comments:

The filing explains, "Neither party disputes that a game is deserving of some copyright protection," before adding, "The game mechanics and the rules are not entitled to protection, but courts have found expressive elements copyrightable, including game labels, design of game boards, playing cards and graphical works."
[/quote]
(emphasis mine)

For what it's worth, you're always at risk of being sued. Anyone can sue you for virtually anything. Now whether or not they win is a separate issue, but the court costs can easily drown you. In the end, you have to decide how much risk you're willing to take and how you'll protect yourself.

For what it's worth, you're always at risk of being sued.

QFE -- Most tetris clones have been shut down simply by the threat of a lawsuit, even though the Tetris company would likely lose in court, because the 'clone' developer hasn't had the money to hire a lawyer to defend themselves.

Trademarks cover names, so if I make "Hodgman's Risk", then I'm infringing on the "Risk" trademark.

Copyright covers "creative works", which usually just means art/sounds. In that tetris ruling, they also covered what basically amounts to the User-Interface layout as a creative work, and that's what sunk the defendant -- they copied they way in which the (unprotected) mechanics were conveyed to the player via the UI.
IMHO, that's a very grey ruling as it arguably violates the precedent of Scènes à faire (i.e. it's hard to express the rules of tertis without using that kind of UI layout), and different laywers/judges could've resulted in a different ruling.

1. Where is the line drawn?
2. Is every clone out there risking being sued and shut down?

1. There is no magic easy answer to that question. http://sloperama.com/advice/faq61.htm
2. You are risking being sued and shut down without doing anything at all!

[quote name='Cornstalks' timestamp='1344047408' post='4966016']
[quote name='hustlerinc' timestamp='1344047167' post='4966015']
On the other hand clones of Tetris are being shut down because they use the same mechanics in their games.

No it wasn't. Read the judge's comments:
[/quote]
But the judge ruled in favour of Tetris company, atleast judging by the title of the article. I don't know what that means as far as consequences go, I just assumed.
[/quote]

Don't assume. Read the whole article (not just its title), and ask your lawyer.

[quote name='Cornstalks' timestamp='1344047408' post='4966016']
[quote name='hustlerinc' timestamp='1344047167' post='4966015']
On the other hand clones of Tetris are being shut down because they use the same mechanics in their games.

No it wasn't. Read the judge's comments:
[/quote]
But the judge ruled in favour of Tetris company, atleast judging by the title of the article.
[/quote]
Yes, the judge ruled in favor of the Tetris company, but not because the clone has similar game play mechanics. I don't know if you even read the article (why did you post it if you didn't read it?) or did any research, but if you have you should have noticed it was the way in which Mino expressed itself that infringed on Tetris (and the fact that the creator openly admitted he was trying to create a clone of Tetris---even the graphical representation of it).

Game mechanics and rules cannot be copyrighted. But expressions can be (like art and music). How you express your game is copyrighted, and that is what Mino was infringing on.

I suggest you read this article on the matter, as they have a lawyer explain a few things. Think of it like this: You hear a song on the radio. You like the song and want to sell it to other people so you can make money (but promise you'll give a little royalty to the creator). Not surprisingly, the owner says no to letting you do that (it's their song, they get to sell it and make money). So you buy the song, listen to it repeatedly, and compose a near exact duplicate of it with your synth keyboard, and then start selling this song to people. You even told people you were trying to make a copy of this song. Obviously you're infringing on the original song's copyright.

You can be inspired by the original song and make your own, but you can't just straight up copy it. At least try to change it a little so people think it's not a straight duplicate.

Also, for what it's worth, Mino (the word) when referred to a falling tetronimo game originated from Tetris: link.

If you make a clone, don't make a straight up clone. Make a variant. Change it up a bit. It's safer. You can't just clone something and expect it to be safe. You can make a game based off Tetris with the same mechanics and rules, but for the love don't actually make Tetris.

At the risk of being 'off topic'-- the example given by Cornstalks regarding music is a bit more complex..
In music, there is such a thing as a "compulsory license" (http://www.copyright.gov/circs/circ73.pdf). So if I hear a song on the radio that I like, I can record it myself (do my own "cover" of it) and sell my version. I do have to pay 9.1 cents/copy to the copyright holder, but they are forced to license their song to me (thus the term "Compulsory" license).

It would be interesting to contemplate something similar for games-- What if Tetris were forced to license those who wanted to make a "cover version" of Tetris. (I don't really think that's a good idea, but it is an intriguing notion, and not without precedent, as the music example shows).

Brian Schmidt
Registration open for GameSoundCon, October 24,25 San Francisco, CA