Jim -
Some of the guys at JLC have been testing this stuff, sticking it in a bucket of water for a week & apparently it doesn't even go soft. Dry it out, you can't tell it was ever wet.
Another guy had a basement get flooded, during those big floods in Jersey this year, and it survived just fine.
On the other hand, it's a b*tch to work with, because of the fiberglass fibers; and having to skim it adds a fair bit of labor to the install.
Still not sure that's what BJ means by yellow board, though: he said it wasn't paperless...?? Hope he gets back to us.