[rincebrain]

DFBSD has substantial kernel differences from FreeBSD (IIRC the original reason for the fork was that the author disagreed about how to implement multiprocessor scheduling and went off to do it his way), such that the diff between the FBSD tree and the DFBSD tree would be enormous at this point. Drivers sometimes make their way between the two, I believe, but it isn't just a copy-paste operation.

Ubuntu and Debian's kernels, on the other hand, are kept as itemized patchsets against the same kernel, and it would be hard (but probably not impossible) to find drivers that build+work on a Debian kernel and break on an Ubuntu kernel of similar age.