I see he's using the program "write" by stylus labs[1].
It's an absolute favorite of mine (Especially on the ipad), and deserves to be more popular than it is.
It's not without rough edges, but it's killer feature: You can quickly reflow your handwritten text to add more blank space in the middle of a sentence, in the middle of a paragraph, in the middle of your paper. Or arbitrarily reorder anything at any time.
To me, it really is the features of the word processor finally come to handwritten text.