GPL does not decide where it's applicable or not - the law does

As for in-ram-linking-as-modification: just look at the modification licence, its framed in terms of conditions that are really only relevant to fixed, distributable copies.

Bingo. And what does it mean? Right: you go back to copyright law. Does it allow this particular modification or not? YMMV. You've been warned.

That this has been the prevailing wisdom for a long time (e.g. the GPL FAQ, that NVidia are happy to distribute binary-only drivers for users to load with their GPL kernel, etc..) suggests strongly that your lawyer's interpretation is beyond the pale.

GPL FAQ says: if Sun will produce internal ZFS driver for Linux GPL will not force a disclosure - Sun will be free to use it internally. Good, but hardly relevant. NVidia does not distribute GPLed code at all - so again, not a problem. As for "prevailing wisdom"... Who's wisdoms is this? Not mine - that's for sure. When at least one distribution was closed over GPL troubles, when Linus says A vendor who distributes non-GPL modules is _not_ protected by the module interface per se, and should feel very confident that they can show in a court of law that the code is not derived, when you can see things like Oh, and at least one major distro has been served with legal papers due to them shipping closed source kernel drivers, and more are on the way (I'm not sure if it was Kororaa or not, but I sure as hell know that Novell wrote Most developers of the kernel community consider non-GPL kernel modules to be infringing on their copyright. Novell does respect this position, and will no longer distribute non-GPL kernel modules as part of future products) it sure looks to me like "prevailing wisdom" says the following:
1. It's illegal to distribute non-GPLed drivers with GPLed kernel. If you are not sued today that only means your time didn't come. Yet.
2. If you are distributing non-GPLed drivers on separate medium you are probably Ok, but be ready to prove this to court.
3. End-users are probably violators too but we don't have money or willpower to sue. The only thing we can do is drop support - and we are doing it.

Basically it means: CDDLed ZFS can not be included in kernel. No way, no how. It'll be infringment - plain and simple. Separate distribution is probably Ok, but watch your back. Oh, and distributors can not include it in distribution too.

Do you really think there are a future for ZFS in a position like this? Permanently ostracized without any hope to be ever included in the trunk and without any support from kernel developers? I sincerly doubt it.

If your lawers claim that when you are interpreting the license you can safely ignore opinion of guys who actually wrote the code under said license and still keep the copyright... then you are beyond caring, I afraid... Linus and Co always said one thing and thing only: we can not force GPL on non-derived work. No way, not how. And this is the only reason why non-GPLed modules can exist.