The name is a bit misleading to be honest. Think of it as a regular, family friendly, music festival with the camping reversed. i.e. mostly campervan fields with a small area for tents rather than the other way around. Even if you don't have a van, the fact that you park up and pitch your tent next to your car is great as you don't need to carry kit for miles. This gives the campsite a different feel as people bring more kit!
Once in the arena its just like any other music festival where the stages dominate and there are food stalls, flag shops, clothing etc.. There is maybe a slight nod to campers but from memory the only ones that you wouldn't see at a 'normal' music festival were: Vantastic clothing, cadac, someone selling VW black out screens, and an awning vendor. There may have been a couple of others but I get the impression that its not about vans.
I've never been to BusFest etc so can't compare but would expect them to be about the vans with some music, whereas Camper Calling is a music festival where a lot of people turn up in vans!
Hope this helps.