[Skubber]

It sounds like you are using the JSGME mod enabler.
Yes?

At the risk of telling you what you already know, the folder in the mods folder can be named anything you want, but then that folder MUST have a data folder within:

MODS/IUB-or-whatever/Data

I pretty sure there is also a standalone milkcow mod that comes included with the newest release of the Harbor traffic mod. So alternately you could just add that to your RUB configuration.
(But IUb is pretty nice if you can get it to run.)