Yes there are plenty of those. And if they then blatantly state that they are not open source because they don't want somebody to build a business on their product while that's exactly what they are doing, then they lost me as well.
I really like what you guys are working on, and I'd absolutely give it a try. But this is really a deal breaker here. Make the team-oriented features proprietary that need server space and accounts and all that, open-source the rest and enable it to run offline. Maybe not tomorrow, I get that. But the moment you do this will open the dams. Until then, you'll stay in a niche.