But I just need a small footer note for my website's engine and not a text in "a real" program (like you can compile with GNU C Compiler). So I use this text instead:
----- Snip: -----
Line: Foobar v1.2.3 Copyright (c) 2003, 2004 by Roland Häder
Line: This website's engine is free software which is released under
the GNU GPL either version 2 of the License. ----- Snap: -----
You'll need the rest of the sentence because you've left the "either" clause hanging.
This is much shorter and will not take so much important space and traffic. Or shall my visitor see just 30% of my website's text and the last 70% is for the (c) note?
I don't quite understand what your engine is and how you're using it on your website. If you're just making it possible for visitors to your website to click on something to use it, I don't see why you need to include a copyright notice for it. It wouldn't do any harm, though. On the other hand, it may be safer to do so, if it's possible for people to download your engine in a usable form from your website, even if it's not your intention to distribute it in this way. If you are distributing it, then you should have a complete copyright notice in your source code, whatever it is.
Laurence