That flag was proposed at several times for use in Germany in the late 1940s, but I believe never actually officially adopted or used.
It was Josef Wirmer's "Resistance Flag" proposal in 1944 - see the following:http://crwflags.com/fotw/flags/de!1949.html#res
It was also proposed 4 years later as a political flag for the Christian Democratic Union Party in 1948 - see the following:http://crwflags.com/fotw/flags/de!1949.html#cdu
It's appearance again is interesting, but it hasn't been associated with any particular political group or movement to my knowledge. I'd be very interested to learn the source of that picture.