Kim Kardashian Sex Tape For Free?

As TMZ first reported, a mystery buyer has approached Vivid Entertainment (which owns the rights to the tape) in an effort to buy it and remove it completely from the market.

But now Pornhub.com, which bills itself as the largest adult website on the planet, wants in on the action. In a letter to Vivid head man Steven Hirsch, the site says they are willing to offer $5 million for the tape ... considerably less than the $30 million Hirsch is asking for.

The site -- which is 100% free -- says they "respectfully disagree" with Hirsch's value of the tape, stating they feel the DVD market is "dying" and online is where it's at.