The idea of FoldingText evolved from:
1. Out of college I got to work on the Jazz ZUI (Zooming User Interface) toolkit and then build it's successor Piccolo. http://www.cs.umd.edu/hcil/piccolo/. For me this was a super cool project to work on. I liked to take notes and tried/build various ZUI notes apps. Great fun but I always ended up using plain text files on my desktop instead of fancy ZUI app.
2. I gave up on ZUI for notes and decided instead to build Hog Bay Notebook, a Mac app for notes. Similar concept to Evernote (but a few years before I think). Database of text files with a full text index for searching. After a few years I was making my living selling this app, but I would still tend to go back to keeping my notes on desktop in TextEdit.
3. Around this time https://ulyssesapp.com added "full screen mode" to their app. Was a popular feature, but Ulysses was a big app with lots of other features that I didn't really want. So I spent a week making WriteRoom 1.0. WriteRoom was a very basic text editor with one feature... that it could zoom into a nice fullscreen mode. It originated the term "Distraction free writing"... so yeah for that! :) This quickly sold better then my notebook program which had at that point I'd put years of work into.
4. This lead me to the conclusion that there's a market and need for simple text based alternatives to "major" apps. Many people saw WriteRoom as a MS Word alternative, even though it was much, much, simpler.
5. At the time 2005/2006 "Getting Things Done" apps were becoming popular, but they were pretty complicated. Lots of chrome surrounding a simple list of tasks. I created TaskPaper as a simple text alternative to OmniFocus. The original versions were just a little syntax highliting built into TextEdit. But over time I wanted a better solution for handling large complex todo lists and so started building in outlining and filtering into the app. After a few years the end result is that TaskPaper is an outliner data model presented/edited through a plain text editor.
6. At this point we get to FoldingText. I didn't want to keep bolting features onto TaskPaper... I wanted it to stay "Plain text todo lists". But TaskPaper's underlying outliner model with a text UI seemed like it would be good a many other things. FoldingText was my attempt to generalize the outline mode/plain text UI into a platform that other's could extend. Along the way I decided to use Markdown as the plain text format that would define the underlying outline structure. I regret that decision. It added a lot of complexity (keeping markdown parsed into runtime outliner model) and made most people think of FoldingText mostly as a markdown editor. FoldingText become a good markdown editor, but the Markdown focus clouded the bigger goal for me.
7. By this time there were 4 of us working at Hog Bay Software. Mutahhir and I worked mostly on FoldingText. And then Mac apps stopped selling so fast and we didn't' have money to continue. Hog Bay Software had to shrink down to only me again. And I didn't have resources to keep working on all the apps. So I've refocused to work on TaskPaper and WriteRoom again. While Muthahhir has taken over the FoldingText project and is working on a big release soon.
Along the way I've looked to lots of apps for inspiration.
Early outliners in particular. But while I like them, they are problematic on how constraining they are when editing... they are field based so you only edit one line at a time. That's why I prefer using the outliner data model, but presented as unconstrained plain text editor.
Besides the history described above FoldingText was most inspired by the Cannon Cat. Maybe not so much in every feature and implementation, but in the large idea of a text based user interface.