Just jumping in on this, not that I’m an expert on GPLv3. The ideal outcome here would be a word from @stoermelder, because we’re in a friendly and functional community that we all value and we all want to respect each other’s intentions and boundaries. But I think the choice of GPLv3 license expressly permits what @Steve_Russell is doing, doesn’t it? The only question I can see is with section 5(a), which @Squinky quoted, and I have a suggestion about that.
For anyone who wasn’t around, the issue that @Squinky is rightly raising to had to do with admission to the VCV Library, because Andrew (not @-ing him because I am sure he’s pretty busy right now) has implemented additional “do not clone” Ethics Guidelines, which I think is a very good thing, and which, now that the “takeover” rule has been removed, would also apply to @stoermelder’s work (absent permission from him). But, as the manual notes, those guidelines may go beyond the legal requirements, and in this case they do. As I understand it: inside the library, cloning is forbidden and plugin and module slugs are centrally maintained; outside, only existing law governs, and for GPLv3 plugins, there are very few restrictions. There’s no attempt here to resubmit the modified plugins to the library under the same slugs (or different slugs).
That said, forking is pretty definitely “conveyance” so section 5(a), which @Squinky quoted above, would probably apply when the code is modified:
The work must carry prominent notices stating that you modified it, and giving a relevant date.
The commits and repo change that @Jens.Peter.Nielsen mentioned above might be enough, but I’d mildly suggest that anyone who is doing this (extremely valuable and community-minded) work should consider adding to the top of the original README something like:
This is a fork of {ORIG_AUTHOR}'s original plugin made on {YYYY}-{MM}-{DD} intended to help the original author with migration to Rack V2, and any modifications will be submitted as a pull request once they are tested. If {ORIG_AUTHOR} would rather these modifications not be made public, they should contact me and I will delete this repo immediately.
This seems to me as though it would satisfy the GPLv3 while being courteous to the original author and clarifying for anyone who runs across the fork, especially if they get there without context. And (as I suspect will almost always be the case) when the original author comes back from vacation/day-job/whatever, they can easily accept the pull request except for the modified README and thank @Steve_Russell or whoever’s doing something similar for all the help!