Regarding Spring, the lobby in question uses Lua sockets and a modified chili.
The chili modifications are project agnostic and will probably be integrated upstream in current or similar form.
All projects also require LCS, which provides a class-based system in Lua (the official repo can also be used instead).
The lobby itself consists of the following repositories:
- liblobby (in-game lobby library, can be used standalone without chili) docs
- chililobby (chili lobby, requires liblobby and chiliui)
- IngameLobby (standalone Spring mod, which uses the other two repos and provides a complete example)
LibLobby Status: alpha
ChiliLobby Version: Unreleased
ChiliLobby Status: WIP, pre-alpha