It's a pretty detailed look at what goes into deciding to implement a FTP model in a game, how specific models are devised, and some of the overall benefits and problems FTPs face in the Western market. On why the FTP may be a really viable option for (good) indie games, Cheng had this to say:
Luckily Nexon has the standpoint that we're not going to release the game until it's a quality game. And in fact, if you get into this business you realize that you can't make money if you don't have a quality game. It's not like retail business where you have to ship at a certain date or you're going to lose money. It's not like that at all. You want this game to keep going and going and going. And also you're not investing huge amounts of money, you don't a 100 person team working on this project. We have eleven people working on this project. And so it's tiny and we're going to keep at it until we have a really good product. And in terms of the fun value, the fun versus the business, I think the key thing to remember is that in this business you have to make the game fun first before you can make any money. And if you take it the other direction you're just going to fail. That's the only conclusion.
It's a meaty interview, especially if you're interested in the FTP model and how it's getting implemented in a wider variety of games than just the stereotypical 'crappy Asian MMO.' We'll have to wait a while to see if it turns out to be a good bet for Sugar Rush, but Cheng seems pretty enthusiastic.
Interview: Klei's Jamie Cheng On Indie Free-To-Play With Sugar Rush [Worlds in Motion]