Alternativas ao iGTD para Software as a Service (SaaS) com licença comercial

• Software as a Service (SaaS)
  Todas as plataformas Windows Mac Linux Chrome OS Android iPhone Blackberry Blackberry 10 Apple Watch iPad Android Tablet Kindle Fire Web Self-Hosted Software as a Service (SaaS) Firefox Opera Safari Internet Explorer BSD PortableApps.com Chrome Microsoft Edge HP webOS Outlook Gmail Firefox OS GNU Emacs
• Licença comercial
  Qualquer licença Licença gratuita Licença Open Source Licença comercial