Where is the line drawn, usually, with inspirations from older... games?

YOU get to draw the line. You draw the line based on your own tolerance for risk. If you are very concerned about being sued, then you draw the line farther away from the original IP. If you are less concerned about being sued, then you can move the line closer.

Forgive me if this is a typical questions that's been asked multiple times ; I've done my best to look around with the Search options, but I couldn't find a satisfying answer.[/quote]

[color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif]

I gave you the same answer everybody else who's asked the same question has gotten. I guess you saw those, and I guess this is still unsatisfying. But it's the answer that can be rightly given. Your lawyer can help you figure out where you want to draw the line you don't want to cross. Nobody can give you a more satisfying answer.[/font]

[color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif]

For more on this (and doubtless equally unsatisfying) there's [/font]FAQ 61

[color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif]

.[/font]

Because I've gone into this topic ad nauseum in the past I'm just going to let what I've written earlier stand.

http://www.gamasutra.com/php-bin/news_index.php?story=26290

However, I still don't understand (but that might be a simple formality) how come there are some many clones of original older ideas.

Because the risk tolerance level of those games' creators was fairly high.
There is no crisp clear line we can give you. FAQ 61

However, I still don't understand (but that might be a simple formality) how come there are some many clones of original older ideas. Even games such as the Great Giana Sisters. Have those case historically ever went to court (and I ask that by simple curiosity)?

Because people draw the line such that they take the risk. Never mind old stuff - even today, the game industry seems littered with similar ideas. (Thankfully ideas on their own aren't covered by copyright.) Obvious commercial examples would be the Civilization clones Call To Power, or the numerous Doom/Quake. In open source, there are many examples (e.g., Free Civ, Widelands).

But then, you could do something entirely seemingly innocent, and someone might sue you because they think they own the word you used (example because someone mentioned "the" AppStore, I presume they meant Apple's app store, which made me think of the recent case over trademarks).

AFAIK, most of the cases I've read about are due to issues with trademarks, or clear cases of copyright (using the original media or characters). Have there been any assertions of owning copyright of things like ideas or game mechanics/rules?

Re: http://www.gamasutra...php?story=26290 - this is a good and useful article so thanks for that - some people on here run a mile as soon as the words "clone" or "remake" are mentioned, but it depends on the specifics - especially if we're only talking about games that are inspired by, rather than direct clones. I did however note:

Creating a video game clone of board games, card games, and the like could create just as many problems. One famous example is the suit brought by Hasbro against the developers of Scrabulous, a well-known Facebook application.[/quote]It's probably worth noting that, AFAICT, the specific issue was the name sounding similar, and not claiming ownership of the rules? http://en.wikipedia.org/wiki/Lexulous suggests they were allowed to continue under a new name? (Not that that disagrees with the point - it is indeed true that copying board games can run into problems.)