Or at least that's how Podiobooks sees it.
Now I'm not a lawyer and even if I was my knowledge of US law would be lacking in this case. The purpose of this post isn't to give out intellectual property adivce, rather it's to impart some common sense business advice.
If you're entering the podcasting field or launching a new service or product then you should seriously consider staying away from product names that contain the word "pod". I know, it sounds stupid and it sounds like taking the easy road out, but if you've got better things to do than be tied up in court with Apple for the next decade, take my advice.
If you feel that Apple is out to lunch (as is the increasing opinion of the intelligent world at large), then fund the fight with money or volunteer time. Don't put your business or domain on the line. Apple is big, hungry, and rich. Probably more than you.