How to play on a MacWARNING: this page is in disrepair and instructions aren't guaranteed to work (but should send you in the right direction).
1. Download https://drive.google.com/file/d/0BwbAiEHn4hRmLVNSeHpoNDBfdUU/view
2. Somehow obtain the correct version of the spring engine. This springrts.com forum thread may help. Find it in the thread or compile it yourself or make someone else compile it for you.
3. Open WebLobby once and close it to create the necessary directories
4. (Mentally substitute the correct engine version for 100.0) Extract Spring to '/Users/username/.spring/engine/100.0' (create the 100.0 folder if needed). Your path should look like '/Users/username/.spring/engine/100.0/Spring_100.0.app'.
5. Open Weblobby, go to "Settings" -> "Login" and enter your Username/Password.
6. Check "Use Zero-K server" under your username/password.
7. Switch to "Games to show in battle list" and select Zero-K.
8. Click on the "Connect" button (top right corner).
If a download fails, just rejoin the game.
If the game crashes, try to following:
- Enable safe mode in settings.
- Go to settings, click Edit Engine Settings and set HangTimeout to -1.
If you have more questions, feel free to post in http://zero-k.info/Forum/Thread/19682 or make a separate thread.