Zim is an open-source desktop wiki application, Its perfect to take notes and organize them together as connect them to each other. It also provides a self-hosted web version. It works fine on Windows, Mac OSX and Linux. Laverna is an open source project released under MPL 2.0 license.

Laverna is a note-taking application offers many features despite it's simple user-interface as note synchronization and backup to Dropbox and remote services, markdown editing, distraction-free mode, todo notes, code highlighting, importing and exporting notes, and powerful encryption for notes. Turtle has powerful features as client-side encryption, markdown support, tagging, powerful search, sharing, browser extensions with clipboard support, TeX math support, file attachment, and RTL (Right-to-Left) support. It has Google Chrome and Firefox browsers extensions. It works fine with Linux, Mac OSX, and Windows. Turtle is an open source note-taking application, built to organize notes, passwords, bookmarks, and images. We have covered special note-taking styles and note-taking editors in this article: 12 Open source Free Note-taking Desktop Apps with Unique Features. We choose the notes with advanced and usable features as powerful encryption, cloud backup and synchronization, private note support, and multi-platform as it can run on Windows, Linux, and Mac OSX. There is free software with a set of features that can compete and win with a commercial solution. Note taking, is a daily requirement for most of us, however, finding a good solution that can compete with commercial ones is hard.

Osx desktop note