[mavus]

I've only recently started using it but if you're looking for something similar but cross platform and open source I recommend: https://boostnote.io

All the core features you would needs from a notes app for developers. It even has iOS/Android apps.

[alunchbox]

Did a quick google search to see if there was anything similar to Quiver that is open source and you beat me to it on posting it :D. How's the experience been using boostnote?