Comment 18 for bug 316247

Sure tags would work for paid apps - just use a "paid" tag on all items that require payment. Those tagged items will only be considered by Sparkle if the app has set to use the "paid" tag somewhere in code. The code could be expanded to have items in the appcast have multiple tags if that's a concern, but the current implementation is generic and simple enough to be useful in all cases I can come up with.

And as I said the only reason I'm pushing on the eta of 1.5 is because of the feature-freeze and backwards compatibility concerns. So many apps are currently using the RC that it seems the current trunk could be released and anything being worked on now could be 1.51/1.6. But of course, the release schedule is completely up to you.