Legal Question in Intellectual Property in California

All creative material that qualifies for copyright is, technically at least, covered by common-law (non-statutory) copyright protection as soon as it is set down in a fixed medium. The step of actually filing for federal copyright protection is necessary before the creator of the work can sue under the federal copyright law, however. The chance of a suit, under the facts given, seems pretty tiny, given that the author would have to register and then would incur lots of costs and nuisance to prepare and file a lawsuit for what would probably be not much in the way of damages.

It's sort of like asking if you are breaking any laws or are you a trespasser if you short-cut five or ten feet across someone's front lawn when walking around a corner at the end of the block. Sure, you are breaking the law and you are trespassing. Are you gonna be sued? No.

I'm quite unsure what the value would be in giving proper credit without obtaining permission. If you know the author, why not ask for permission to use the material?