I talked to the Rhodes guys at Railsconf and have looked at Rhodes a little. First of all, they told me that if you OSS your app, you get RhoSync for free, tho

I talked to the Rhodes guys at Railsconf and have looked at Rhodes a little. First of all, they told me that if you OSS your app, you get RhoSync for free, though I don't see that on their site. I'm pretty sure that you could write a perfectly fine app without RhoSync. I think RhoSync is for making it easy to sync data between your servers and the app (and it can send a push notification to tell them they have new data), but I don't think there's any reason that you couldn't just use normal practices of querying APIs and stashing that data in the database.