Further research showed me that I could change the default location with this line of code:
Scheduler.Codebase = "/js/dhtmlxscheduler"
However, this only sets the rootfolder, so all the files have to be located within this folder. I helped myself out by putting empty files over there and call my own styling and scripting from the location I wanted (just to get rid of the console errors).
So this solved my problem (as far as it could be solved).