Mavericks owner Mark Cuban tweeted a link to the site Thursday, writing: "Gotta love Mavs fans!"
The home page plays a song and doctored photos include James' face on a J.R. Ewing picture and him dunking over the Dallas skyline.
The Mavs are a perennial contender with superstars in Dirk Nowitzki and Jason Kidd, with whom James won a gold medal in Beijing in 2008. The team could easily free up cap space for a sign-and-trade deal with the Cavaliers, who, if forced into a deal, would prefer sending the marquee free agent to the Western Conference. James also is a big Cowboys fan.