Forum OpenACS Q&A: Response to Time for a name change?
If there's any right time to make a clean split from ArsDigita, it is now. The founder is gone (along with his vision), the mission statement has changed, the toolkit is different, etc. Ultimately you will be better off in the long run and in the short run, a Google search will find OpenACS anyhow.
The 'net (and business in general) has a very short memory. In a year or so, no one will care if you changed your name from Architext to Excite or Mosaic Communications to Netscape (or you are now called Novartis, Verizon, or Accenture).
I don't know the state of OpenACS 4, but I'm assuming that there still is some convention in using ArsDigita-related stuff out of habit (e.g., ad_my_neato_proc_name).