Copyrights and Licensing 

...Excerpt out of User Guide of the FSX Mission Editor ...

The mission system command  extension  (simvar.exe) may always be used in any mission  for free. It should not be distributed on its own, only with a mission you have written that requires it. It may also be made available  by the publisher  (FSAddon) as a separate download, which you can refer to in your installation  instructions.  However, it may only be  distributed with   your   missions   provided   you   are   entitled   to distribute the mission itself: 
- If you are using the free version  of the editor, you may use it to create   missions   which   are   themselves   distributed   for   free.   You   may distribute the command extension with your missions. 

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