I'm talking about allusions to books, films, etc...like using a line from a film, slightly altered so that the player recognises it but it's not exactly the same.Like in Discworld Noir. I've seen most of the films and I recognised the scenes and linesÃ, but they weren't exactly the same. Is it still under copyright laws?
I doubt it. It could simply be termed a 'Homage'. ;D
Alluding to/paraphrasing a line from something isn't copyright infringement. It falls under acceptable use.
You're only breaching copyright when you use something from another source, call it your own, and sell it. If you credit the source, and ask permission and get it, then you're okay.
But as far as taking a line or quote, that won't hurt a thing.
If you don't try and sell it, I'm pretty sure it's legal to use other peoples stuff without even giving them credit...is that right?
Here's the rules, at least in Canada.
You can use up to twelve consecutive words from a copywrited work and still be able to claim it as "your own." This covers most cliches, commonly used phrases and sentences that just happen to be identical. After that, you are required to properly attribute it to it's original creator or at least get permission.
If the work is in the public domain (as in the creator has been dead for 50+ years, it was originally meant to be a public resource, plus a few other situations I'm too lazy to look up) do what you want with it. Just don't try and pass it off as your own work.
Just alluding? Go nuts. Just don't claim it's yours.
Also, if you're parodying something, the laws change completely. There's a bunch of laws that allow parodies to be sold, though I wouldn't be able to give any more information on it.