Rudy Huyn, the dev behind all these apps, tweeted yesterday that he's working on porting 6snap to Windows 8!
P.S: There's no such app as 6vine. It's 6sec!
Think I read a tweet from Rudy that he was porting the code(at least for the 6snap app) to "universal app" which Microsoft introduced at build this year AKA, it should launch in the Windows 8 metro store once it's done..
You don't need one... Just pin the instagram website to your home screen. Its metro enabled like th wpcentral web page, so you get a nice instagram logo an it takes you straight to the web page.