I accidentally ordered priming sugar from Austin Homebrew. I force carbonate. Isnt this just extra light DME? Can I use it as my starter sugar instead?
No, AHS's priming sugar is corn sugar. Of course, you could use any kind of sugar you want for your primer, including white refined table sugar. So, yeah, you can use it for your starter batch if you want...just don't use more than one packet, as too much can give you that nasty cidery taste.
I wouldn't use it for a starter. You'll get the yeast acclimated to consuming corn sugar (uber-fermentable) rather than extract. You could slide the corn sugar into the boil (in moderation) in a receipe you wanted to have a little bit more of an alcohol kick; it'll full ferment, so it won't add any body. But, I would definately not use it for a starter, the yeast that are most dominant in the starter will be those best suited to consuming corn sugar, not maltose.
Yeah, what the bird said. Use DME or your canned wort (if you canned any) only for starters. The yeast get used to the simple sugars in corn sugar and then have a hard time fermenting the complex sugars in your wort.