a) Give prominent notice with each copy of the Combined Work that the Library is used in it and that the Library and its use are covered by this License.
Public domain and freely available artwork is commonly available on the internet. Free movies are not. One of those seems more likely to be valid than the other.
And in any case, Sony can use this artwork commercially. It's free software, for goodness sake. What they missed was the requirement for attribution. So they should provide that somewhere. End of story.
I don't understand this kind of logic. I mean, I can see the hypocrisy argument -- Sony is a Big Evil Corporation and constantly harping about IP rights, and here they got caught not-quite-following-the-letter-of-the-licesense.
But come on now: the KDE team drew and released those icons (and the rest of their software) with the clear intent that they would be useful to people in their own work. They even licensed it to allow that. This isn't a great crime, it's just a mistake.
I honestly think we should be pretty strict about following licenses to the letter. No-one who creates open-source software has the time to hand-hold all their users and make sure they are in compliance, so we should help them out.
http://www.iconarchive.com/show/oxygen-icons-by-oxygen-icons...
It says there "commercial usage allowed". They probably didn't even know it was from KDE.