Well he did post this in 2009. I've seen them around on various blogs aswell but they all lead back to or credit this guy. You say you don't know who made the originals.....could it be possible you got them off one of these blogs and just didn't check where they originated? He's also written tutorials on how to make HDRI's so the fact he would then go and steal someone else's doesn't make sense to me.
A big thanks for those HDRi files, they have been very useful in many of my renders. I placed them in my favorites and I am giving you a llama badge for them. I am also recommending them to other people cause they are very,very useful indeed and big time savers.
I am a Chinese. First,my English very bad.Few days ago，I search for some good HDRI online，but I can't find them in our country‘s web page ，so I'm here.Then,thanks for your free HDRI. My job is make animation for our company with Maya,I want some friends who would share more questions with me in Maya. Cause I leaned Maya all by myself.Freecourse,Free resource.If you're interested or you can help me，My E-mail ：firstname.lastname@example.org