From a Reddit Question and Answer with Greg Boyd:
What’s the most common misperception people have of open theism? How do you address that?
LOVE that you asked this! The most common misperception of the Open Theism, at least as I espouse it, is that it is about the scope of God’s knowledge rather than the nature of the future. Its reflected in the many critics who claim Open Theists “deny omniscience.” The truth is that we all affirm God is omniscient. The issues isn’t how much God knows, but what is the nature of the reality that God knows. And the only distinctive claim of Open Theists is that the reality God exhaustively knows INCLUDES POSSIBILITIES. Precisely because God is omniscient, who knows things exactly as they are. So he knows possibilities AS POSSIBILITIES, and actualities as actualities.