YouTube cofounder had piracy concerns

That bit of intrigue was among the confidential information that had been kept under wraps since Viacom Inc. sued YouTube for alleged copyright infringement of “The Colbert Report,’’ “The Daily Show,’’ and other shows in a federal court in New York.

The newly released evidence also revealed that Viacom wanted to buy YouTube before getting beat out by Google Inc., which acquired the site for $1.76 billion in 2006.

Viacom, the owner of Paramount Pictures and cable TV channels that include Comedy Central, sued YouTube in 2007, seeking more than $1 billion in damages.

The company, in which Dedham resident Sumner Redstone has a controlling stake, alleges that YouTube allowed copyright-protected clips to appear on the site in its early days to attract a bigger audience. YouTube maintains it has always obeyed the Internet’s copyright laws, which generally protect service providers from copyright claims as long as they did not post the infringing material themselves and promptly remove it when notified about a violation.

An e-mail exchange less than six months after YouTube’s February 2005 inception showed that Chen was worried Jawed Karim’s lax attitude toward copyrights might cause trouble.

“Jawed, please stop putting stolen videos on the site,’’ Chen wrote in the July 19, 2005, e-mail. “We’re going to have a tough time defending the fact that we’re not liable for the copyrighted material on the site because we didn’t put it up when one of the cofounders is blatantly stealing content from other sites and trying to get everyone to see it.’’

YouTube said Chen’s e-mail was referring to aviation videos that had been making the rounds on the Web: “The exchange has nothing to do with supposed piracy of media content.’’

Karim left YouTube before Google bought it in 2006.