> If the only differing bits were the portability framework, this would just be a matter of adding missing support. But it isn't — the FreeBSD object file Nvidia publishes lacks the internal symbols used by the Linux driver.

In fact it is. For Linux and FreeBSD Nvidia distributes exactly the same blob for compilation into nvidia.ko; the blobs for nvidia-modeset.ko are slightly different. (Don't take my word for it, download both drivers and compare kernel/nvidia/nv-kernel.o_binary with src/nvidia/nv-kernel.o.) Nothing is locked in the closed source part.