[Yaa101]

You cannot change a copyright notice of a GPL source, GPL allows you to distribute, it even encouridge you, but nothing in the law allows you to change copyright claims. GPL follows copyright laws to the letter, that is it's strength. Forging copyright notices is a form of deceit and if I am right copyright laws will say that it's theft.

[Natsu]

I don't know about calling it theft, but some courts have made it into a DMCA violation, though there is disagreement on that point.

[Mikeb85]

The copyright belongs to you as long as you don't convey the program. GS didn't convey it, so it belongs to them.

https://www.gnu.org/copyleft/gpl.html

[camperman]

Nonsense. The copyright belongs to the copyright holder. I know GS like to steal every fucking thing in sight but claiming copyright on a piece of Free Software just because its received a copy is a new low.

[rdtsc]

Wait I think we are getting confused here. What code are we talking about here.

Copyright of code belongs to the author of the code, or a company that employs him.

If they took say GCC and then replace copyright notices on it, it doesn't become their code, they are using it under a license from the original authors. Replacing a header in a file doesn't magically give you complete control and copyright over it. That would be silly and it would nullify most of the open source software licenses.