It is a Minecraft PVP client/modpack.
You can download the mods raw or you can download the modpack in both Curseforge and Modrinth formats (Support for downloading from them comming soon).
The installer is no longer supported, but more ways to install may come soon.
As of now there is only 1 version and that is 1.19 which is based on Fabric. More versions may come at a later stage.