I happened to recently come across the following linked article by Bruce Ware on the topic of whether Open Theism is properly classified as evangelical. (link) Ultimately, I agree with what I understand his conclusion to be, namely that the doctrines of open theism are not evangelical doctrines. They compromise the nature of God.
Of course, they are also not Reformed doctrines in consequence of not being evangelical doctrines.
Ultimately though, we should be cautiously charitable in approaching professing believers who hold such errant views as open theism. There is an important difference between people simply being in error (due, for example, to inadequate teaching), and those who stubbornly resist the truth. By correctly identifying open theism as outside the evangelical walls, we must be careful not to insist that everyone must have a perfect understanding of every aspect of the nature of God in order to be saved.
I don't think Ware was trying to suggest anything to the contrary. Indeed, reading Ware's article, one can sense the tension in Ware, who would prefer to include Pinnock and other open theists within the walls of broad evangelicalism.