Ok, thanks for all the comments. So I might throw out "env_root" or "env_dir" or "install_dir" or "install_env_dir"... but, when it gets to be a sane time (currently 7:30a here) I'm going to crowdsource suggestions from a bunch of people here (who know nothing about the specifics behind this ticket) and see if they can come up with anything better.

I don't particularly *like* namespace either... but on the other hand, I'm not sure there's anything I like more and isn't confusing. I'll see if I can come up with anything better today.