The reason Paul Graham used Lisp is it was the only reasonable way at the time to implement RTML, which was the HTML macro language with online editor that Viaweb was built out of.  RTML was how every website in Viaweb was constructed, it is what allowed them to move quickly and customers to customize with unequaled flexibility.<p>It was their key competitive advantage and Lisp was critical to its creation and function.  It would be foolish to attempt to implement RTML in something else.  Perhaps slightly less foolish in 2015 but not by much.