Unclear whether license is either `GPL-2.0-or-later` or `GPL-2.0-only`

i've checked a bunch of catfish source files, and all of them have this license header:

#   This program is free software: you can redistribute it and/or modify it
#   under the terms of the GNU General Public License version 2, as published
#   by the Free Software Foundation.
#
#   This program is distributed in the hope that it will be useful, but
#   WITHOUT ANY WARRANTY; without even the implied warranties of
#   MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
#   PURPOSE.  See the GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License along
#   with this program.  If not, see <https://www.gnu.org/licenses/>.

this header makes no mention of allowing versions of the GPL later than version 2, therefore going just by this, catfish's license is GPL-2.0-only

however, i then found this line:

    license='GPL-2+',

so there's something of a contradiction here, what is the correct license for catfish?