Hey Philip. I've never personally seen any purely free wifi on the subway (unless someone's left their egg unlocked!), it's only the wifi that you mentioned which is tied to the phone companies. Wifi isn't offered at subway stations either. I personally would love to see this change though - especially with the Winter Olympics coming up in a couple of years, a lot of people will be travelling around Seoul too.
Seoul is going to change that. Starting next year we'll see real free WIFI (provided by the city): http://english.yonhapnews.co.kr/business/2016/02/23/96/0504000000AEN20160223009200315F.html
Great news! I just hope that bolster that networks so its actually usable. I know I've had really bad experiences with just trying to connect to public wifi in central Seoul and Incheon International Airport.
Hi guys. Thanks for the insight and the article. Personally I've always had a good experience with the airport wifi, particularly compared to those in other countries where it is often unusable. I recently read an article about the NYC subway only going into trial for wifi on their trains—maybe this was on the Kojects Twitter, come to think of it. At any rate, a citywide blanket of public wifi would be impressive, if it works, and especially if it's easily accessible for tourists.