I'd just like to interject for moment. What you're refering to as Mastodon, is in fact, OStatus/Mastodon, or as I've recently taken to calling it, OStatus plus Mastodon. Mastodon is not a network unto itself, but rather another free component of a fully functioning OStatus system made useful by the pubsubhubub, salmon and ActivityVerb components comprising a full OStatus servicer as defined by OStatus.