Forum OpenACS Q&A: Response to OpenACS vs ACS API difference

I think you are comparing ACS 4.x with OpenACS 3.x? That API
difference exists between ACS 3.x and ACS 4.x too!

OpenACS 4.x will have that new DB_ API just as ACS 4.x does; but right
now OpenACS 4.x is still in early development.  If you are in a
position to help with the OpenACS 4.x development, the code is
available via anon CVS.  If not, you'll have to stick to the
ACS/OpenACS 3.x API for now if you want your modules to work in the
currently released OpenACS.