Well, first off, in this context they're using free=libre not free=gratis. (Free as in freedom, not free as in free beer).
Second, there are a lot of contexts where MIT's educational materials are available for free (gratis). I've taken a lot of MIT courses over the years and never paid a dime except to purchase a hard copy of SICP.
Second, there are a lot of contexts where MIT's educational materials are available for free (gratis). I've taken a lot of MIT courses over the years and never paid a dime except to purchase a hard copy of SICP.