So all Wordpress plugins are supposed to be GPLv2 or higher. We'd like to fork a plugin that currently integrates with one system and change it to integrate with a different system. There's a readme.txt file with the following in it:
License: GPLv2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
The version on GitHub is much older than the version on wordpress.org so we'd like to base it off the wordpress.org version. Usually, GPL licensed code has the GPL header in every file, but none of the files in this plugin - except for the readme - have any headers at all. From what I've read, putting the notice in every file is recommended but optional.
I'm assuming that it's still ok to fork it? We'd give credit to the original author and release it on github (under the same license). But it would be far newer code than the author currently has on Github.
Just want to double check since I'm fairly new to the GPL license and releasing open source code based on someone else's code.