Tammy: That would be the CVS HEAD you checked out, which is probably going to become 4.7. To get 4.6 you need to specify the tag on the cvs checkout command line:
(omitting the -d cvsroot location -- add it back in for this to work)
cvs co -r oacs-4-6 (I think that's the right tag, but it may not be)
Without the -r option you get the CVS development HEAD, whatever version that happens to be.
Andrei: Regarding the ACS=1 information. That is correct; I had not thought of the fact that OpenACS would say 'you need to update' instead of 'your PostgreSQL driver doesn't contain the extra functionality required by OpenACS'.