I'm surprised aD clients would want something Tcl & not Java these days. In any case, though there is no "formal" OpenACS entity there are over a half dozen companies
that one could rely on for OpenACS work, not to mention the community as a collective whole. I would think that ought to be fairly comforting to someone who is risk averse. One or more of the above companies companies could disappear and there would still be options and ongoing active development.