The current server could be installed as database server only.
According to the INSTALL doc, the only required modules are:

DBD::Pg (version 1.32 recommended - see admin/depend.pl)
DBI
String::ShellQuote
LWP::UserAgent (only if you're going to set up a replicated slave)

However with the NGS server you need nearly half of CPAN () just to import the dumps in your Postgres db.