It should depend on dev-db/postgresql-base instead. Reproducible: Always
I haven't been able to find any documentation stating that dev-db/postgresql-server is required. It doesn't appear to install any modules for the server to use. The assessment of the reporter appears to be correct: Only dev-db/postgresql-base is required.
+ 10 Mar 2013; Sergey Popov <pinkbyte@gentoo.org> freeradius-2.2.0.ebuild: + Change optional postgresql dependency to dev-db/postgresql-base wrt bug + #456900. Thanks to Oleg Gawriloff for discovering this issue