LegacyMC is a launcher I am currently working on that has all the Minecraft Beta, Alpha, Infdev, Indev, Classic and Pre-Classic versions of the game. It's not just a launcher on the website you can get the server software for all these versions PLUS the craftbukkit server software for Minecraft Beta PLUS some archived plugins, LegacyMC is mainly something that brings back Golden Age Minecraft!
There will be no authencation to a microsoft account since all versions before the full release, version 1.0 are free so anyone that can not afford Minecraft or just wants to have a Legacy Style Launcher then this launcher you. Since there is no authencation sadly you can not play on servers because it just does not work with everybody having the same name, but in the future I may add a authencation system if you want to sign in to a microsoft account to play on multiplayer servers.
For this launcher my plans are to make it to were you can play on multiplayer servers at some point, but my main plan at the moment is getting the launcher in a stable state where you and everybody can download it and enjoy golden age minecraft versions I also plan to have a feature where in the launcher there is a server list where you can put in the server ip and it look like modern day minecraft server list but for the older versions of minecraft.