I think it's more that if the BSD guys are interested in keeping gnome available for BSD, they have the freedom to port it, or implement the interfaces that gnome requires/expects.
If GNOME really wants some fancy Linux feature, they can ask BSD to implement it.
And the BSD developers don't have the manpower to do that.
Is there a history of such requests going unserved?
See Project Utopia, ALSA, DRM, KMS, cgroups, etc.
BSD and Solaris cannot afford to keep up with Linux. They just can't. So the question is whether Linux people should subsidize OSes that they don't use or just let them fail.