Tracks is described as 'web-based application to help you implement David Allen’s Getting Things Done™ methodology. It was built using Ruby on Rails, and comes with a built-in webserver (WEBrick), so that you can run it on your own computer if you like' and is a Note-taking Tool in the Office & Productivity category. There are more than 100 alternatives to Tracks for a variety of platforms, including Windows, Mac, Android, iPhone and Online / Web-based. The best alternative is Joplin. It's not free, so if you're looking for a free alternative, you could try Standard Notes or Evernote. Other great apps like Tracks are Simplenote (Free, Open Source), CherryTree (Free, Open Source), NoteLedge (Freemium) and Trilium Notes (Free, Open Source).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.