I'm sure this info is covered in a thread here or there, but I was chatting with someone about how some of the mods work online the other day, and I thought I'd clear up any misconceptions.
First - I create and maintain an installer that includes most of the commonly used mods in Demigod. You can read about that and download it here: http://forums.demigodthegame.com/399399. That is pretty much where you want to start if you are interested in learning about what mods we have and getting the latest versions. I work pretty closely with the modders, so if they release an update, I typically have it added to my installer within 24 hours. Sometimes I'll host a game online indicating that there has been a new release (so that folks that don't frequent the forums can get the most up-to-date versions).
Anyway, that said, here are some important things you need to know about the mods.
First, there is a difference between installing a mod and enabling a mod. If you install a mod, that means that you downloaded it and ran the executable. Just installing a mod doesn't mean that its "turned on" or enabled. It simply means that the mods will be visible to you in the in game demigod mod manager. To enable a mod, you have to open that in game mod manager and enable each mod you want to use 1 by 1.
Hosting a game and joining a game - the difference in mod speak
You can join any game that has mods enabled even if you do not have those mods enabled yourself. All that matters is what mods the host of the game has enabled. You only need to have the mod installed to join. If you don't have a mod that the host is using installed, you won't be able to join the host's game.
So, the host decides before hosting a game what mods he/she wants to enable. Then, only folks with those mods installed can join. If you are finding that no one is joining your games when you host with mods on, its quite possible that folks do not have those mods installed and cannot join your game. Just keep in mind that YOU do not need to enable any of those mods if you are joining. You just need to have the mods installed.
UI mods are different
UI mods are not like the other mods. Anyone can have them installed at any time. Installing and/or enabling UI mods will not keep you from being able to join a game, etc. So, feel free to always keep those enabled.
This last bit can be annoying, but certainly worth explaining. Games can desync before the game starts or very shortly after the game begins when using mods. This is actually caused by the way some modders setup their code at one point. For instance, let's say I create a mod. You download that mod, install it, and enable it. 2 days later, I make a small change to that mod and reupload, but I don't change the version info or "key" that is used to identify the mod. So, I host a game using my mod. You are able to join my game because it looks like you have the same version as me. So, we start a game and then the game quickly desyncs. This happens because if there are differences between the versions, Demigod can detect those differences and force a desync. These sorts of things happened from time to time when the mods were seeing very frequent updates. And its actually the main reason I decided to create my combined installer. That way, if you make sure you are using the latest version of that installer and that everyone in your game is using it, you won't encounter any desyncs caused by mods. If you are in a game where a desync occurs (again, at the load screen or 2-10 seconds into a game), just ask everyone in your lobby to download and install the combined mod package, and that should sort you out.