I can't find anything GPLv2-only.
On the top of most of the source files:
HP2xx is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY. No author or distributor accepts responsibility
to anyone for the consequences of using it or for whether it serves any
particular purpose or works at all, unless he says so in writing. Refer
to the GNU General Public License, Version 2 or later, for full details.
Therefore, should be: LICENSE="GPL-2+"