TYPO3 is Open Source Software and therefore of course free to use and download. But having some money available for development, travel expenses, motivation and loads of other stuff helps TYPO3 a lot.
The TYPO3 Conference T3CON09 offers you as a company the opportunity to contribute to the TYPO3 project in many different ways. Sponsor the event with money to place your company logo in prominent positions or donate stuff or services your company offers. Find out more in the "Become a sponsor" section.
Your support as an individual is also greatly appreciated. Why not help with all the small things during the conference as a "helping hand"? Or just donate 10 Euro to do your tiny bit for TYPO3?