GPL - a invalid license choice?

[Jens Seidel]

Hi,

a few patches for hex-a-hop contain the following header:

# Copyright (C) 2007  Sam Hocevar <sam+deb at zoy.org>
# Licensed under the GPL, see /usr/share/common-licenses/GPL

Does the license (GPL) make sense? What is GPL?

The link refers to GPL version 2 which makes sense for me. But not to
specify the version seems just wrong.

I even read short time ago in Linux Magazin that something as
"GPL version 2 or later" may be invalid as a person cannot license
a work under a future license (GPL 4, ...) because he doesn't know
the content of it.

Comments?

Jens