For one I feel more accountable for getting this project over the line. Isoflow has around 19 stars at the time of writing (at least I know there is some pull on the project, which is something I thrive on). I'm splitting time between isoflow.io the site (which I'm rewriting at the same time - but which will probably be deprioritised), and the open-source diagram editor. There's certainly a sense of my target market shifting from diagram makers to developers, who will care a lot more about the API design. Pacing is super important, as a full-time engineering manager with two kids, I can (and want) to only set aside max a couple of hours a night to work on Isoflow. I'm finding I'm majorly productive over those two hours (although today I've let time get away from me).
All in all, things are moving ahead. I predict between 2 to 4 months to get to a v1. You can track progress on the actual repo (I've just added a very simple roadmap in there as well).
I'll be working to release Isoflow under the MIT license, you can find the start of the open-source project here at https://github.com/markmanx/isoflow (feel free to star!). If you have any tips or questions for me, hit me up on Github for a chat!