The press release from Redfin makes it sounds like they are happy to still lease out the data for 5k+ requests a month; everything below that being free it seems

"Redfin is boosting the number of “calls per day” from 100 to 5,000 before partner companies have to start paying for the data."

http://www.geekwire.com/2014/redfin-buys-walk-score-marking-...