Portfolio has been a program that we have been looking at for a while, I think in our case it may just be a good solution (other than having our programers write us a new software application). I guess the two main things we were really looking at in Lightroom were the editing functions and the handling of a large workflow of RAW files. We are currently a PC based operation using the CS2 suite, so my thinking for a consideration of including Lightroom was more along the lines of general compatibility.
No it doesn't, and you'd be better off looking at Portfolio for this sort of work. It handles the multiuser requirements and is more geared to general asset management than LR. So it would be easy enough to expand it with fields for rights and usage details. Doesn't mean it can't be done, but you're going to need all sorts of special keywords and workarounds to do it in LR. Alternatively, if you have database admin people, you can hook up Lightroom's database via ODBC and connect it to Access or Filemaker databases which would contain the rights and usage info. But that would be a bit of a house of cards. Portfolio handles such tasks easily.