License Clarification

[scottbot95]

I am trying to get this package imported into nixpkgs for use with NixOS. Part of that process requires knowing the specific license used for this package. The COPYING file is for GPL2 but to import a package into nixpkgs, I need to know if the license is restricted to GPL2 or are newer versions allowed. This requirement comes from the GNU recommendations which recommend you explicit state the allowed variants of the GPL that can be used.