It doesn't show it alternating flapping and gliding, though, the gliding footage is just of it gliding. Look at the rest of the footage, it keeps flapping its wings until it stalls. It doesn't seem to be able to control its flight path.
Yes, but it physically can flap to fly, and it physically can glide. Making it do so alternately is just a matter of software.
Not that I'm underestimating the difficulty of bird-control software (especially in wind), but I think the most difficult part of this invention is the physical mechanism and getting it to fly at all.
Oh, I agree, that's why I think they'll be indistinguishable from real birds in a couple of years.