See the Scratch Credits page for a list of those who contributed to the design and development of Scratch 2.0.

http://scratch.mit.edu/info/credits/

Mitchel Resnick, Natalie Rusk, John Maloney, Paula Bonta, and Brian Silverman made up the core design team for the Scratch 2.0 editor, with contributions from Shane M. Clements and other members of the Scratch Team.
 
John Maloney was the lead developer through Fall of 2013, after which Shane M. Clements took on that role.