Some random thoughts about #TiddlyWiki, which is - in my opinion - a very interesting piece of free and open source software targeted at end-users.

http://tiddlywiki.com/

It's a personal note-taking app which can be stored in a single HTML file (including JavaScript code and content).

The TiddlyWiki file can be saved locally or uploaded to a server, and it can be encrypted end-to-end. Installation on Node.js is possible, too, with slightly different features. 1/

Despite its qualities, #TiddlyWiki is probably going to stay niche for the following reasons:

1.) Many of its features require inserting code (markup) into the text fields.
2.) Many features aren't very well documented.

With regards to 1.), TiddlyWiki isn't very different from MS Word or Excel, in my opinion. They often require macros, and Excel formulas can get quite complicated, too.

However, MS has greater market(ing) power, and documentation tends to be better, too. 2/

Bottom line: Poor usability and complexity are important reasons why free and open source software often doesn't get widely adopted. However, we shouldn't forget that proprietary programs such as MS Excel can have steep learning curves, too. People are just more used to them, and it's easier to get help. 3/
@stefanieschulte
One of the nice things about a program like TiddlyWiki is that some enterprising developer can expand on it, making it easier to use, and possibly more well documented without having to ask anyone's permission.