Thanks! I also found the following one which gives a rationale [1]. The fine distinction is that the patent grant is completely separate from the copyright license and the termination of patent grant has no influence on the copyright license whatsoever. Unfortunately these messages are not in a single thread, so it is a bit hard to find them.
And after actually reading it he said it's okay to use for GNU projects: https://lists.gnu.org/archive/html/directory-discuss/2017-01...