Got this from here: http://www.devmaster.net/news/index.php?storyid=1263 'PhysX SDK Free for Commercial and non-Commercial Use Posted by: Kenneth Gorking at Nov 15, 2006 12:46:07 Public Releases Thread: Free PhysX for all!! Posted on 10/27/2006 6:36 PM We have just implemented a new EULA (End User License Agreement) that allows the PhysX SDK, from 2.6.0 and on, to be used in all commercial and non-commercial PC projects for free. In order to qualify for the new license, you must: 1) Fill in all of the *required fields in your user Profile ("My Settings->My Profile"), as some have changed and others now require accurate, up-to-date, information. NOTE: Your name is the only identifying data visible by default to other users of this site, and only if you choose to post to this Forum. 2) Accept the EULA when it pops up after selecting the related downloads. I have added extensive pop-up descriptions to each of the required fields, in case there are any questions about how to fill them (hover your mouse over the ? buttons). If you do not follow these steps, you do not have a valid license to use the PhysX SDK for any purpose. Note that this free license applies to PC versions of the SDK, including the Windows and Linux platforms. You need to contact us directly if you require the Xbox 360 PhysX SDK for a commercial title, or contact Sony for the PS3 PhysX SDK. If you have already downloaded the 2.6.0 PhysX SDK for evaluation, you can activate the free license by following both of the steps above. The timestamp of your new download stored on this system will validate that you accepted the new EULA.' Ok, so no 'Mac' anywhere to be seen... BUT, and it's a big 'but', if there _was_ a Mac version, that would preclude the need to licence the current physics engine, and maybe bring the entry price to Unity down... Although there is nothing wrong with the current engine! Thought I'd save the Unity guys some cash... Cheers, Luis.