The project seems still alive and active, at least according to its recent RFC'ing from LKML [0].
For some more information, Phoronix also recently wrote an article [1] about it, also the GitHub repo [2] seems to be somewhat active (last commit was 06-02-2020).
Ah, you're right, it does appear to be still alive. If anyone from the popcorn linux team sees this, please consider updating the outdated portions of your website (and getting an HTTPS certificate). Had I never read this comment I would have gone on unaware that the project was not dead.
For some more information, Phoronix also recently wrote an article [1] about it, also the GitHub repo [2] seems to be somewhat active (last commit was 06-02-2020).
[0] https://lore.kernel.org/lkml/cover.1588127445.git.javier.mal...
[1] https://www.phoronix.com/scan.php?page=news_item&px=Popcorn-...
[2] https://github.com/ssrg-vt/popcorn-kernel