This package is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License version 3, as
published by the Free Software Foundation.

The reason you don't have the usual "(at your option) any later
version." option is that the file `src/freenect-server.c` contains
code from the freenect project, which is dual-licensed under the GPL
2.0, and the Apache License 2.0.  We can provide it under the GPL 3.0
because the Apache License 2.0 is compatible with it.  We can't know
if this is true of later versions of the GPL until they are written.
All other files are licensed under the GPL 3.0 with the option of
using later versions.  It is likely that you can use this under later
versions of the GPL.

freenect, as of the time I took code from it did NOT include a CONTRIB
file.

Unless you are getting the distribution from git, the full text of the
GNU General public license should be included in the file
`COPYING.GPL3`.