Yes DIBOARD architecture are similar. But diboard was created becouse of bad code and lack of important architure solution for pull and push messages.
DIBOARD much more thoughtful than nntpchan.
>>we pull posts from them but they don't back.
DIBOARD and NNTPCHAN are open for passive reading with XOVER and ARTICLE command. For PULL AND PUSH in both directions you must exchange public keys and confirm connection.