Another alternative, admittedly not open-source, is Recollectr (disclaimer: built by me.)
Recollectr was inspired by prior projects like Notational Velocity but aims to be a lot more - omnibox, markdown support, reminders; and for paid users: revisions, note-linking, and sync. I built it because I felt like other note-taking apps just weren’t fast enough and they broke my concentration.
It’s quite late here but I’d be happy to answer any questions tomorrow!
Thanks very much for letting me know; I’ll look into this! They’re all videos so perhaps there’s some encoding issue with Safari on iOS.