The project has a homepage: http://hpo.ornithopter.net/
Under "technical info", it says
The key is to produce enough thrust with the wing to keep the aircraft flying at the required
forward velocity. This thrust is produced by placing the wing at a lower angle of attack,
relative to the local flow velocity, on the upstroke, and at a higher angle of attack on the
downstroke. It can be seen in the figure below that this results in a large amount of lift
and thrust on the downstroke and a small amount of lift and drag on the upstroke. The net
result is positive lift and positive thrust.
Throughout the stroke the wing must twist with the proper magnitude and phase to produce the
proper angles of attack. This is accomplished passively by designing the structure in such a
way that the aerodynamic and inertial forces produce the proper twist.
So, this is NOT merely a glider.
The up flap does NOT cancel out the down flap
The wings' movement is NOT purely vertical, there is a twist component.