So heres a guide for mac users:
1. Download spring 100.0 for OSX and my modified version of Spring Web Lobby
http://www.felix-kraus.net/files/zero-k/zero-k_OSX.zip2. Open WebLobby once and close it to create necessary directories
3. Copy the extracted directory "100.0" to '/Users/username/.spring/engine/'
4. Run WebLobby again and click on "Try ReactSWL (alpha) (can connect to Zero-K server)". You'll have to do that each time you launch WebLobby.
5. Go to "Settings" -> "Login" and enter your Username/Password.
6. Switch to the "Advanced" settings tab and set lobbyserver to "lobby.zero-k.info".
7. Click on the "Connect" button (top right corner).
If a download fails, just rejoin the game.
Feel free to ask me when you have problems.
Enjoy :)