As you can see in this techworld post.
Apparently they are using the GPL licensed muPDF library and link it against their proprietary PDF viewing application. If that is true, then it would be a very straight-forward, FAQ-type violation. muPDF is not LGPL but GPL licensed, thus you cannot create derivative works without licensing them under GPL, too.
The whole license management and even software release management at Palm seems to be very sloppy. For example, based on the object code and disassembly, I can prove that the source code for libpurpleadapter on opensource.palm.com does not (or no longer) correspond to the object code that they ship.
What's particularly surprising is that Palm actually is forcing Artifex to go to court over this issue. You would expect such a straight-forward issue to be resolved fairly quickly and settled out of court, before it ever escalates or turns into a PR disaster.
You would expect a company that is regularly building and releasing firmware images to have an automatic process that packages the source code as part of the build process. In fact, Palm uses OpenEmbedded to build their images, and it is a standard feature of OpenEmbedded to create the corresponding source tarballs for everything it builds.
Furthermore, the Palm kernel contains several binary-only modules that indicate MODULE_LICENSE("GPL") in it - which is clearly not true. If you inquire about the sources, they will respond that they will not provide the sources.