[mikestew]

Maybe I'm pointing out what you've already discovered, but the file format is documented: https://msdn.microsoft.com/en-us/library/dd924743(v=office.1...

Given that, are you looking for something pre-baked, or is the file format enough to roll your own?

[fluentcar]

I saw that page and wasn't sure if I would be competent enough to roll my own parser of that format, hence my search for an existing .one parser or some similar open source format from Openoffice or some other open source note taking format.