Jürgen Moltmann, a German Reformed theologian who is Professor Emeritus of Systematic Theology at the University of Tübingen is an Open Theist (although the Open Theist controversy seems to be uniquely American).
From Roger Olson:
At first he was as always a bit reserved, but after perhaps five or six glasses of wine he became downright talkative. (The university hosting the lectures did not pay for the wine! I think the dean paid for it out of his own pocket! Moltmann, of course, did not know that.) I asked him about “open theism.” He asked me to explain it to him which I did. His response was: “But of course! That is part of the kenosis of God!”