The entire thing was written in C# with ASP.NET Core for the server, and (sorry) WinForms for the Admin Panel and the launcher. And it integrated quite nicely with the authentication for the web application that was being developed. At one point I was thinking of LDAP support, but I left that job before I could implement it. It has a fully functional license key system (no DRM, gotta implement that yourself), branching, and an announcement system.
As far as I know, it's still running and fully functional after leaving a year ago, with the actual ASP.NET Core server having about a year of uptime.
I have been considering making some QoL changes and creating my own open-source launcher, but I haven't had the time or the mental capacity to do that.