btw is an open-source note taking & personal website builder.
Athens is a knowledge graph for research and notetaking. Athens is open-source, private, extensible, and community-driven.
Joplin is an open source note-taking app to capture your thoughts and securely access them from any device. You can take notes, make to-do lists and sync notes across devices by linking it with cloud services like Dropbox. The synchronization is protected with end to end encryption.