Hi Dean,
I just compiled my TruckOff demo using FPC and did not get any error messages. Having said that, I think I may have found your problem.

In your ODEImport.pas file do you have a function declared "dWorldQuickStop". If so this should actually be "dWorldQuickStep". If you change it to dWorldQuickStep it should compile and run fine with FreePascal.
Maybe a stray find and replace or typo crept into your version, because the CVS version correctly has the dWorldQuickStep declaration.