My understanding is that GPL-2.0-only and GPL-2.0-or-later only differ in their "Standard License Header". The actual license text should be the same.

Here we don't have any license headers, so I set GPL-2.0-only, to be on the safe side. Richard Stallman wrote about this (https://www.gnu.org/licenses/identify-licenses-clearly.html): "[...] I decided to give each developer a choice about allowing future versions. This meant developers could release a program under GNU GPL version 1 only, or release it under GPL version 1 or any later version. The way developers state their choice is in the license notice that goes at the start of each source file. That's where the GPL says the decision is stated." Later he writes: "Please put on each nontrivial file of the source release a license notice of the form shown at the end of the GPL version you are using."

My reading is that unless the license notice exists, we can't assume that the -or-later variant is intended.

Aaron Puchert (aaronpuchert) - about 5 years ago

author source maintainer

README.TXT says "The metamath program is copyright under the terms of the GNU GPL license version 2 or later." So you're right. I'll change this.