The good news is it's possible to host your own mare. Plenty of people mirrored the code before it was removed, such as https://github.com/MareSynchronos (not mine).
For the server you'll need to know how to use Docker. There are a few services e.g. Redis, Auth, the discord bot, and you'll need NGINX too. The client plugin is banned from running in Dalamud but if you just rename the assembly you can get around that.

Of course this is too technical for most people so perhaps in a few weeks someone will package it up nicely with a freshly renamed plugin and a server.bat or server.exe. We might find ourselves in a world of decentralized private mare instances for every community/FC.

>>718844417
This is just to ban any version of "MareSynchronos" by wildcard. The ban mechanism was already in place and being used to block execution of deprecated plugins or incompatible old versions of things that could crash your game. It is controlling of the Dalamud devs to do this but it's quite understandable given that they're one legal letter away from having the whole project collapse and they've always tried to maintain distance between their approved plugins and 3rd-party cheats/risky stuff. As I said it's very easy to get around the ban by just renaming Mare.