I think the most open is Dennis. Progress reports and open source release. He made the hw, the sw despite a horde of people saying it's impossible..
Yes, I agree that Dennis is as open, or more so than MikeJ, but IIRC, he did not announce the MiniMig until it was almost finished (a smart thing considering all the people that torched him and said it couldn't be done).
MikeJ, on the other hand, has been more open and provided more updates to information about his project from start to finish. He is not releasing his product as Open Source, so naturally needs to keep certain information private, to keep someone else from stealing his design and making it into a product before he has a chance to produce and sell his boards.
From his comments and tone, I would guess that if MikeJ ever tires of this project and moves on to something else, there is a good chance that he will release it to the community, if he no longer wishes to pursue a commercial path with the product.