"Was there a prohibition against using the VK due to copyright infringement? I remember seeing them a lot at one time but then they were gone."
Not to my knowledge.
The O.G.s started disappearing, either by passing away, or election disagreements (mostly), until what we are left with today.
There were many that had left over election disagreements (which used to be very common)... There are some that no one knows what happened, they just stopped posting (being who they were, it is assumed without saying it, that they either became bedridden and/or passed away).
There are some here that just aren't active like they were back then, for their own reasons.
Considering that the majority of them now would probably be 75+ years old (I am one of the younger ones at 55yo...), I can understand that they are making their lives more useful ;^)
There was a time when I was having financial issues, between 2014-2016, and my computer had crashed, so I had no access to the internet/FR.. so I missed a couple of years.. but I am pretty sure that most of the VK slowdown had already happened.
That's why a couple or 3-4 years ago, a few of us discussed (and I am sure someone still has the link to the thread) bringing it all back. I lost the link, but that thread ended up going on for weeks, and I can't even remember how many posts there were, but it brought many of us back together, and a few of us always working behind the scenes discussing patterns of known trolls/retreads.
I wish I still had the link to that thread (and if I can get it, I will bookmark it again).