I spent a bit of time a while back getting the DBPro ODE plug-in commands up and running in DGDK. The final result was a set of release and debug libraries which I released on the following thread:
http://forum.thegamecreators.com/?m=forum_view&t=114688&b=22
Download the second release if your planning on trying it!
It suffers from some inherent bugs which were present in the plug-in and not everything seems to have been properly implemented but if all you want is a simple physics engine to play around with then it works reasonably well and appears to be stable. I didn’t have time to start re-designing it and bug fixing over and above just getting it running in GDK.
I integrated it into my game engine and have been using it for some time to get me by until they release DarkPhysics for GDK.
I have not provided documentation other than installation and configuration notes but there are examples of the plug-in use on the forum. Look at the library header file for the available functions etc.
Otherwise, download the ODE source code or precompiled libraries (available on the net) and integrate them into your project as Tempicek suggested. But your dealing with the raw interface with this option, the plug-in code encapsulates it to some degree and presents a higher level interface to the user!
No matter how good your code is, someone will improve on it