DD> Are Network Coordinators on 'zone:net/0's meant to run a BBS or DD> message base ?
No.
DD> Or do they just need to run a mailer that does nothing but hold DD> packets ?
They must receive uncompressed .pkt bundles uploaded directly using one of standard FTN protocols (those described in FTS-#### publications) and perform their duties as described in the FPD.
DD> Is there any restriction to using 'zone:net/1' ?
None. There are two reserved node numbers that should be used by a newcomers (first is /9999, second is /-1 aka /65535), but the common practice is to use existing point address when requesting a node.
-- Alexey V. Vissarionov aka Gremlin from Kremlin gremlin.ru!gremlin; +vii-cmiii-cmlxxvii-mmxlviii