(Reposted from the Mirror Discord server)
For whatever it’s worth I’ve made a copy of the Mirror web app: https://mirrorprotocol.nfshost.com
It’s based on the last snapshot of mirrorprotocol.is taken by archive.org and it should work exactly the same.
As for building from source, it’s more complicated. The README is outdated and misleading but even if you build the app successfully, it doesn’t send transactions to the Station wallet correctly. I’ll try to look into this issue some time next week.
https://mirrorprotocol.nfshost.com was the first fully functional Mirror webapp site created and published after the official sites went offline on 28th October (the official websites came back online after about 2 weeks). The idea of using an archive.org snapshot was borrowed by other sites and those sites were aggressively promoted on this forum as can be easily seen.
Since 20th November https://mirrorprotocol.nfshost.com is no longer based on an archive.org snapshot. It’s built directly from source (the build script and patches are available at https://mirrorprotocol.nfshost.com/buildfiles). Other than the official websites AFAIK this is the only fully functional version independently built from source.