I don't think dedicated servers work with the steam version.
They do
If you
are using the steam version, right click blockland in your steam library, click properties, go to set launch options, then type in
-dedicated -gamemode Custom
Once done that, start your game like you normally would. A console should pop up. If it does, you'll see it loading all of your add-ons. Wait for the console to show:
Authentication: Sending response...
Authentication: Connecting...
Authentication: SUCCESS
Posting to master server
Posting to glass server (*if you have glass*)
Once thats done, right click blockland in the steam library again, go to properties, set launch options, and delete everything in the box. Then, open up blockland, and it should be on the server list. If it is on the server list but you can't join it, click Query LAN and join it from there.
If you aren't using steam
and i wasted my time making this tutorial, make sure that blocklandlauncher.app is in the Applications folder, and try /Applications/BlocklandLauncher.app/Contents/MacOS/BlocklandLauncher -dedicated -map skylands in terminal again.