I finished the implementation of the two way sync (Sync changes made on the device back to the server). Please check it out on your setup/servers, and come back to me with your findings (write to tasksync@gmx.at). Note, it is still alpha so I recommend that you backup your data.
enhanced two way sync with Apple iCloud
enhanced CalDAV Server configuration testing
enabled to delete tasked in the widget
added slim widget display mode
display tasks that are planned for farther in the future