I share my objects for free and I don't want anybody to pay or donate for them. They may be recoloured if possible and included in lots if you think they are well enough. You may upload them in your lots to any free site except the Exchange.
I spend many(!) hours of work on my vehicles and the meshes are handmade from scratch. Therefore don't claim them as your's if you clone the mesh or use it as a base. You have my permission to do so. I'm convinced that these things are made to be used. So, add a simple note within the object description, that's enough and hopefully not a hard restriction.
There might be some special rules on single objects for special reasons. Please respect them! - Thank you.