Legal Issues using Linux in embedded projects
The intricacies of using the GPL license have been hashed out repeatedly in many other forums. [references would be nice for major issues]
This page has a few specific issues relating to embedded use of Linux.
EXPORT_SYMBOL_GPL for kernel USB API
In January of 2008, Greg Kroah Hartman submitted a patch to change the core USB API to EXPORT_SYMBOL_GPL. Here is some information about that change: