DayPilot Lite doesn't show the "DEMO" label. If you see the DEMO label it means you are using the Pro version - if you have tried it previously in your project the DLL (DayPilot.dll) might be still cached somewhere.
You can verify the exact version and number being used by opening the HTML source of the page in the browser. Look for a line that looks like this:
/* DayPilotLite: DayPilot, Version=5.0.307.0, Culture=neutral, PublicKeyToken=null */
This is the signature of DayPilot Lite version 5.0.307.