The latest beta is 2 years old. Most blog comments on Andy's website too.
Is there a new version, living somewhere else? Or an alternative to Sparkle as a whole?
It works for me now, I'm just wondering if there are going to be any further updates to Sparkle, or the promising SparkleCaster app.
It's very much alive. See the Q&A site for the Sparkle framework here. You can ask your question directly to Andy and he'll answer you pretty quickly. The git repository here is actively maintained, too.