I don't see himself distingusihing himself from "members of the Forge" - which furthermore would be dishonest, wouldn't it, if the forum for his game was based at The Forge. (Unless you are working with some other definition of "message board member" that I'm not familiar with.)
Frankly it seems to me that he is trying to avoid being tarred with the Forge's brush, despite selling a game which strikes me as pretty "indie" by any typical measure (eg player protagonism via metagame mechanics that hook onto fictional positioning of PCs), because there is a degree of Forge hostility in many RPGers that I personally don't really understand.
I wouldn't be surprised if that feeds into the motivation a bit, but in the case of Fate, much of its original development
as a game happened without much direct Forge/GNS influence.* Evil Hat,
the company, benefitted (I would presume) from using the Forge resources as the incubator they were intended to be. As I mentioned elsewhere, Evil Hat also produces other games which appear much more influenced by GNS theory.
I think in this case that fundamental part of the problem is that calling something a "Forge game" has come to mean a lot more than just "indie". Forge fans seem to want to give the site credit for anything rpg and "indie", even though other indie games existed before the Forge. I would hope that you are not claiming that the Forge is responsible for inventing the ideas of player protagonism, metagame mechanics (still hate that phrase), or using fictional positioning for either. On the other hand, Forge's detractors use the term pejoratively and ascribe it to a lot of the often inscrutable rules sets that came out of that think tank.
Which is correct? Heck, I dunno. However, I do have a problem with your second paragraph above. Painting "indie" and "Forge" as synonymous is, I think, simply not correct. At the very least, there are gobs of OSR games out there that patently reject the Forge, even simply as an incubator. I also do not think that Evil Hat/Fate is the only pairing of Company/Game that used the Forge as a business incubator, but not a game/development/design incubator. (Although, Evil Hat/Fate appear to be the most successful case...the others on my hard drive appear to have been "on hiatus" for several years.) I have
suspicions about how and when this might have been a small trend, but that's getting even farther OT than we already are.
*The last time I saw anyone attempt a serious GNS analysis of Fate (this was pre-Fate Core), their conclusion amounted to "this game should be dysfunctional."