Burnett has explained that he has "wanted to provide a clean set of data to share with the world" for quite some time to provide both, together, as it gives "great insight into user behavior and is valuable for furthering password security."
But he's done so with some trepidation and much justification (and, before you panic too much, he believes most of them are now dead). "I think this is completely absurd that I have to write an entire article justifying the release of this data out of fear of prosecution or legal harassment," he writes on his blog. "I had wanted to write an article about the data itself but I will have to do that later because I had to write this lame thing trying to convince the FBI not to raid me."
Although researchers typically only release passwords, I am releasing usernames with the passwords. Analysis of usernames with passwords is an area that has been greatly neglected and can provide as much insight as studying passwords alone.