Amazing!! All our dreams came true 
I clicked in the demo (from the readme) but it’s still IP 1.x. Would be great to have a live demo to suggest some features.
Also I think a migration tool will be needed. I’m not a developer and can’t help there but I suggest a crowdfunding to boost it up. I’ll be the first one to donate 
PS: I remember also Fusion Invoice had a community website with lots of plugins and templates from third parties. I’m open to pay for some features as long as they remain opensource (yeah, it’s compatible). In the end, developers need their rewards too.