I've taken a quick look at this thread and there seems to be no mention of it, but there's a
Multiplayer mod for Rimworld now.
Here's a video.
I've played it with ~12 simple mods and it worked nicely. 4-5 desyncs in 6 full, straight hours of play. Desyncs can be solved in a minute by letting the mod try to figure it out itself, or even quicker by having the host re-host the game (exit game to menu and host again) or the clients reconnect (exit game to menu and reconnect).
Here's the download page for the Multiplayer Mod.Here's the installation info for the Multiplayer Mod. Unpack to your /Mods folder, activate and play..that's it.
Here's my collection of mods I'm testing MP with.I can post my Mod Manager Modlist later for quick sharing/loading of mods. Today I added ~17 more to the list (still untested) but the more mods it support, the cooler it is.
It can support multiple people in a server. This is amazing.
Of course, it's not on Steam workshop yet because it's experimental/early, but it's more stable than some AAA games' multiplayer and took me less time to setup than a modded Minecraft server (a good
modpack one that I decide to tweak usually takes 1-4 hours, this took me 5 minutes).
Note that there's some conflicting info about what works or not in Multiplayer. Some people say that Caravans don't work, but there are videos on Youtube clearly showing a player messing around in another map tile with a caravan while other is playing in their main base. If you're really interested, try it out for yourself first.