Appcastr 0.1 for Mac is available as a free download on our software library. The software is included in Developer Tools.
From the developer:
Appcastr is a simple utility for Mac developers who publish updates using the Sparkle update system (or any other update system that uses Appcasting to publish updates). Appcastr provides a GUI interface for creating and editing appcast files that is slightly easier & quicker than just editing the raw XML file. Appcastr is currently in the early stages of development and is targeted towards making appcast files for the Sparkle update system.
You may want to check out more Mac applications, such as CVSServerSetup, jKaiUI or K8055 iOS Bridge, which might be related to Appcastr.