Commercial Use :
If you are using the Debugbar in a commercial environment, that is for professional use, you can try the debugbar for 60 days, and then you must buy a license.
Why should I buy a license :
DebugBar is not free for commercial use, so purchasing it for such use will keep you legally compliant.
We get all our revenue from our sales.
Buying a license will give us the opportunity to enhance the debugbar more and more, giving you the best product for your web developments.
Personal Use :
If you are using the Debugbar for private use or educational use, it is free to use.
You can simply click on the button "Private" when validating the debugar :