Alternativer til Bookis for alle platforme med open source-licens

• Alle platforme
  Alle platforme Windows Mac Linux Chrome OS Android iPhone Windows Phone iPad Android Tablet Web Self-Hosted Software as a Service (SaaS) PHP jQuery Windows Mobile Slack Microsoft Office Outlook Chrome Google Calendar Sunbird Google Apps Microsoft Exchange Server Apple Calendar
• Open Source-licens
  Enhver licens Gratis licens Open Source-licens Kommerciel licens