You should have a look at http://www.groowiki.com
We plan to have the access control features you miss, it is on the roadmap. We also target search, workflow support and right now you can add description to the file and directories
using radeox and write plugins in Java or Groovy.
And yes, I am affiliated with Groowiki. I wrote it and plan to develop it further. And it is free AND commercial as well. Only a very few features are closed (not open) source so big companies needing those specific features support its development.
