According to Olive Tree and Laridian, their products (BibleReader and PocketBible) support PPC2K3. According to Laridian:
Laridian®, Inc. today announced that its PocketBible®, and other Bible-related software is compatible with Windows Mobile 2003 software for Pocket PCs, Microsoft's newest version of software for Windows mobile-based devices.
Go Here:
http://www.laridian.com/ce/news.asp?fullStory=062803
Olive Tree has a "Supports OS 2003" beside the PocketPC bar.
Go Here:
http://www.olivetree.com/