I believe by "no copyright infringement" he means no copyright infringement from Warner Brothers, who definitely have jurisdiction over all their recorded releases. Otherwise the copyright goes to Linkin Park, theoretically. The only defense, and I am no lawyer, I can think of is to say Warner is not the copyright holders of these performances and cannot sue him. Linkin Park must be the ones to file the lawsuit. I think that's kinda taunting the bull here, but it might reduce the number of songs he might have to pay for, and I doubt LP would attempt to sue...
I don't think the LP.com archives go far enough back, but I recall distinctly in December 2002 a post by Mike Shinoda on the news page, right after LPU 1.0 ended, saying that if fans cannot get a hold of the HTEP, then they can download it. His post was followed by a track listing of the CD. This is one reason why I don't think LP would be inclined to sue.
Where it might get foggy, imo, is those internal Warner demos. They might or might not count. I don't know what was hosted on LPI but those demos might have been there. And of course, I cannot tell the exact details of LP and Warner's contract, and so I cannot tell how much power Warner had over LP's works. Or whether or not LP have any copyright power over their songs.
I think it's woth considering. Then again, i wrote it.
In copyright lawsuits, you are guilty until proven innocent. That isn't what it says on paper but it how it typically goes down in court.