There have been no updates in ages (including the promised one for GDPR compliance) and GitHub issues stay unanswered by @clavaque. Unfortunately, the lack of maintenance means that there are already lots of warnings with PHP 7.4 and things will definitely break with PHP 8.0.
So is Comment Mail officially dead? If so, I ask you to release the last Pro version under the GPL (including the CSS and HTML and JavaScript files) so that the WordPress community can take over updates. Right now, I can fork the repository on GitHub, but the license forbids making it available to the public (interesting question: Does forking count as distributing here?) without excising all non-PHP content, which is practically impossible.
In case Comment Mail is not dead (which would be great, I don’t really have time to maintain another large plugin, but I have not found a better solution for double opt-in comment subscripts), when can we expect a new release?