I just downloaded OmniOutliner-r276751-Test.dmg as I was hoping to see sync.omnigroup.com integration. I currently enjoy OmniOutliner Pro both on my Mac and on iOS, but without the macOS version supporting Omni Sync Server, I find myself reaching for other tools.
Thanks for asking, and sorry nobody’s answered before now!
On macOS, OmniPresence is a separate download, as you can combine multiple file types into a single location, rather than being limited to the iOS model of documents being tied to a specific application.