Forum OpenACS Q&A: Re: Will Dr. OpenACS survive? Or why I stopped worrying and learned to love the .LRN consortium?

I think install and TCL are both non-issues to some degree. Look at Rails -- even less people know Ruby than TCL (is my guess; certainly neither is mainstream) but people learn it because Rails is just that cool.

AOLServer OTOH is relatively big. It means you have to be a fairly solid sysadmin to get OpenACS running, and you need a more expensive virtual-root setup instead of a shared apache one. Hobbyists won't bother.