Built and flown in as experimental aircraft only, and the proposed variant with cabin
actually can be regarded as a project, so I moved it here.
Thanks for the link to the pdf-file, it explains the ideas behind it quite well, I think:
The canard wing principally had an adjustable airfoil, working fully automatic, without any
possibility of interference by the pilot. The forward upper part was spring loaded, and pressed
down by the slipstream. When the aircraft stalled, the canard wing developed no lift at all,
so the nose of the aircraft would drop. With the angle of attack decreasing, the wing would
gain more and more a smooth and low airfoil again. This system was not only meant to avoid
stalls, but to alleviate gusts, too. Budig also claimed, that headwinds would automatically lead
to a reduction of the angle of attack, so to a decrease of drag and in a higher airspeed.
As a side note, the article says, that those Budig designs weren't true canards, because they
still had a conventional tail.