I think gcc is still in base, right? They just added clang and set that as the default, AFAIK. I haven't kept up with FreeBSD much in the last few years, so not sure what the plans are to remove gcc.

Also, a quick look at the source tree shows there are still some other parts as well. GNU binutils, GNU diff, dialog is GPL, etc. See: https://github.com/freebsd/freebsd/tree/master/contrib

In the kernel, I think there are some drivers that are based on the Linux GPL code, for example: https://github.com/freebsd/freebsd/blob/1d6e4247415d264485ee... (just first hit from GitHub search for "gpl")

So yeah, looks like there's still plenty of GPL code in FreeBSD that's not trivially replaceable. The same applies to OpenBSD, although in general the OpenBSD people tend to be a bit more proactive in replacing GPL code.