The author's claim that a wide variety of PDAs can share the same software packages doesn't ring true with my experience. I recently bought a Zaurus 5600 and have had a lot of difficulty trying to install and run software on it. This includes packages reported to run on the Zaurus 5500, a machine identical in screen resolution and many other specs.
This is a very frustrating experience for the end-user. It's tempting to look for someone to blame, but you can't fault a free software developer for not having the resources to ensure that her software runs on every device and OS version.
However, it might be possible to harness the power of users to provide broad compatibility testing. The sites that distribute software (eg http://www.killefiz.de/zaurus/ ) should add a place for each package's creator to list the systems on which he has confirmed it installs and works. The site should also include a compatibility feedback section for each package, where users post their device info and whether they could install the software.
This kind of system would save a lot of frustration for end-users, and help developers produce truly portable software.