If you see, all the double process has one common id 3936

ps -ef |grep 3936 will show all the application open right now.

ls -l ls -l /usr/bin/Calendar
lrwxrwxrwx 1 root root 13 Dec 17 12:34 /usr/bin/Calendar -> maemo-invoker

They all point to maemo-invoker. and this maemo-invoker is part of Maemo Launcher. Maemo Launcher is used to launch all application, 1 part being the invoker to start the given program and other being the launcher that initialize most of the data used by program.