The dependency stuff will be largely handled by the 4.0 package manager - ACS version dependencies, not PG, which should be OK. PG version dependencies will be global to the OpenACS version, most likely, given that much of the datamodel and many of the utility routines are shared. 4.0 will probably require PG 7.1, for instance, unless we choose to ignore the new outer join functionality which will probably appear in that version!
