I just wonder...
What is the legal status of doing software remakes?
Ie. all these OpenSomething, FreeSomething etc. clones. Mostly game clones.

Is one allowed to just take all the ideas, behavior, look-n-feel and do an exact (or very similar) copy of the application?

I think as long as you don't break copyright, e.g. by including copyrighted images or sounds in the download, then you are usually OK. You can tell people how to extract the copyrighted material from their own copies of the games.

You might want to ask at somewhere like http://retroremakes.com/forum/

Providing you're not actually copying either the code or graphics then you're clear on copyright law, so it's then down to patents/trademarks. Well-known characters will probably be trademarked (Mario, Sonic, etc), as will the game name itself, and aspects of gameplay (or the techniques behind them) may be patented.

The overall look-n-feel of a game (particularly a simple one) can also be protected ("trade dress"). See this Tetris lawsuit for an example.