The main reason we kept Oracle support in OpenACS is because it became clear that ArsDigita's version of the ACS (Classic) Tcl was not long for this world. Instead of maintaining *two* projects (ACS/Oracle, and OpenACS/PostgreSQL) which never made any sense, we chose to maintain one (OpenACS/Oracle-or-PostgreSQL).
Other reasons why OpenACS is a good choice: there's a real community of developers working away at any little bug, building new features, and optimizing OpenACS far beyond what ACS Classic Tcl did. That's not so much because we're all that smart: we started with ACS Classic Tcl, and we improved from there.
Behold the power of open-source....
