ThinkingRock is described as 'open source and multi-platform software for Getting Things Done - the stress-free productivity methodology and international best selling book by David Allan. [ http://en.wikipedia' and is an app in the Office & Productivity category. There are more than 100 alternatives to ThinkingRock for a variety of platforms, including Windows, Mac, iPhone, Android and Online / Web-based. The best alternative is Joplin, which is both free and Open Source. Other great apps like ThinkingRock are Standard Notes (Freemium, Open Source), Microsoft OneNote (Freemium), Evernote (Freemium) and Simplenote (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.