Small Powerful Brushless Motors
It's hard to say what are the specs, but speculating on the size of the battery pack, it's probably a 14.8V lipo battery pack. P = V * A, P=2KWm , 2 motors therefore P=1KW  -> 1KW/14.8 =~67A. This is a relatively high performance brushless motor setup and it is not surprising, given the mass it is supposed to be moving (180lbs is a good guess for a human). 

I bet their motor setup is custom designed to maximize efficiency so you won't find on the market the specific motors they are using. All that said, if you plan to do something similar, go with Scorpion Systems motors, designed in Germany and manufactured in Hong Kong, which are really good motors. You will need two motor speed controllers (ESC) and a way to generate a PMW signal as input to the ESC so to control the motor speed. See the specs of the speed controllers. Typically hobbyists use these motors for radio controlled devices .. so you can use a cheap transmitter/receiver setup, cost like $30 these days.

http://www.scorpionsystem.com/ ... you find distributors all over the web. 
These are not cheap motors ... there are cheaper brands. Check HobbyKing.com Look for 14.8V (or 4 cells) motors. You'll need to find a motor with a Kv (number of revolutions per 1V of applied voltage) such that you get the required power at the desired spin rate of the motor , which depends on how fast you want the wheels to spin ... Ultimately what defines the power demand on the motor is the load .. and this is where this boostedboards guys are doing the hard part ... there is almost no way to limit the load ... the user does not know how much power he/she is demanding, because it depends on how fast the wheels spin and how steep the road is. 
These guys are probably designing a speed controller smart enough to self control .. when Amps goes too high, it will likely reduce voltage before burning the entire system, which can happen quite fast. 

It is an interesting idea and project... even though I wouldn't put my feet on an electric skate board ;-)

Please note that they use the electric motors as dynamic brakes. Standard ESCs available on the market won't let you do that ... not sure if there is such thing as an ESCs able to use the motor as dynamic brakes. 

Hope this helps.
Regards