I'm not sure I would trust a Russian mirror if the author didn't post it. The main issue with this extension is it has to be updated very regularly. To continue to bypass the paywall requires constant tweaks & edits. So, unless someone makes a fork & wants to take over the project, mirrors aren't particularly helpful.
I wasn't aware of the bpc-clone, but it's working and was updated 4 hours ago. I would imagine Github would catch onto that one rather quickly. The parent folder is private.