It's not that reasonable: the Apple EULA requires things that directly conflict with the GPL, such as the EULA requiring non-distribution of the binary.
So there is that.
Was this statement before the mosh repo gained the COPYING.iOS file and the iOS-related waiver from the OCB patent holder (July 20, 2012)?
edit: was this tweet http://twitter.com/panic/status/195938318536544257
OCB is no more proprietary than RSA was when it was still under patent protection (throughout the '90s, I believe), the reference implementation is public, and Mosh incorporates the reference implementation into its GPL source. The algorithm is well-documented in the research literature, and the implementation is available under a free software (though strong copyleft) license.
Well, thats the point of it.
No, they do not. In fact, the example you gave is exactly the example given by the FSF to explain why this does not occur.
http://www.gnu.org/licenses/gpl-faq.html#CanIUseGPLToolsForN...
It's not a conservative reading so much as an incorrect one, and it's also nothing to do with v3 versus v2. The concern about v3 is that it means that companies are not allowed to use patent or hardware restrictions to do an end-run around the GPL's user protections.
The "viral contamination" FUD has been around for over a decade at least; it's nothing to do with version 3.