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/