Using swiftkit is pretty much same as using any other browser. No bans, warnings or anything. Swiftkit is acctualy part of zybez, and zybez is official jagex approved fansite.
I'd double check your statement. Zybez is no longer an approved fansite; for whatever reason. It has been censored ingame and is no longer allowed to be talked about on the forums.

Might actually download swiftkit to see what it's like i heard theirs usefull tools on it.

