If you want to go risk-free, try PhysX.

Maybe not as advanced as Havok but, IMHO, easier to use. And free.


"The AGEIA PhysX SDK (binary) is 100% free and available right now for download by developers. ...

Free SDK Package:

* Most Current PC Binary
* Commercial & non-commercial use on PC
o Must keep registration information current
o Must agree to the EULA at the time of download (pops up prior to download)
o Available for Windows & Linux
o No PhysX hardware optimization requirement
* PS3 platform (through Sony pre-purchase)"