Sure. But it's worth having a FreeBSD box (or VM) that you can use to tinker with the kernel.

Recompiling FreeBSD kernel source is super easy, by the way. It comes in /usr/src on your machine and all you need to do to reinstall one with your changes is "make buildkernel && make installkernel" . Actually understanding the sometimes decades-old source code, on the other hand, might be a little more difficult...