If they are the sole copyright owners (no external contribution) or have SLAs, they can for any future version of the software. It is not uncommon, it is just hard as most doesn't have SLA to do this.
I know who you're replying to. The premise that gary-kim laid out is still the relevant context. The hypothetical you're laying out, on the other hand, is not relevant, it's at odds with that premise (not in "agree[ment] with him"), and it's derailing the thread. (Which is the same reason your "future versions, not past versions" is downvoted, for that matter.)
Right. _they_ were not meant to be Wiki.js, but ANY open source project. And was a meant to indicate the same subject as _any_ in this reply:
> I don't think _any_ of the mainstream open-source licenses allow you to retroactively revoke or change the license.
My reply is in this context, not in the parent's parent which you mean as _relevant_ context. If I wanted to include the parent context the reply would be more specific. This was a direct reply to a specific message. This is a very normal way to reply on the internet, HN is not special.