Dlls are great but if people get their hands on it they can use them too. I guess BRL has taken this into consideration.
Of course. I'll leave the main question for Mark/skids to reply to, but b3d.dll is a copyright-protected file for which you need a license to re-distribute, so anyone looking to release anything developed in this way will still have to buy a copy.
Releasing b3d.dll with software while not owning a copy of the SDK -- which provides the license to re-distribute the DLL -- is copyright infringement, regardless of whether the software is freeware/commercial or anything else.