It's not uncommon to see BSD developers upset that someone takes their project, does a few modifications, and then releases the resulting work under GPL, such that the resulting improvements can no longer be incorporated back upstream BSD, creating a one-way street.
KernelTrap has an interesting article in which Theo de Raadt discusses the legal implications of the recent relicensing of OpenBSD's BSD licensed Atheros driver under the GPL. De Raadt says, "it has been like pulling teeth since (most) Linux wireless guys and the SFLC do not wish to admit fault. I think that the Linux wireless guys should really think hard about this problem, how they look, and the legal risks they place upon the future of their source code bodies." He stressed that the theory that BSD code can simply be relicensed to the GPL without making significant changes to the code is false, adding, "'in their zeal to get the code under their own license, some of these Linux wireless developers have broken copyright law repeatedly. But to even get to the point where they broke copyright law, they had to bypass a whole series of ethical considerations too."
I've recently noticed that the licence under which SSLeay was released, on which OpenSSL is based, on which LibreSSL is based, has the following addendum after what looks like a standard original 4-clause BSD licence with the advertising clause (which, I must add, is already incompatible with the GPL due to the presence of the aforementioned advertising clause).
* * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */
To avoid the problem at its root:
Why don't the BSD developers add back the advertising clause, to make sure that their licence is incompatible with the GPL Public Licence without saying so explicitly?
Or, alternatively or additionally, why don't they add an addendum as above to their own BSD/ISC/MIT/etc BSD-compatible licence?