Porter, 21, joins the club as a free agent after leaving the Clarets by mutual consent.
Manager Keith Hill said: "George is a good player, he has pedigree and he's technically very good.
"I think it's a great signing from our perspective because he's already got games under his belt this season with AFC Wimbledon.
"He'll also bring pace - a ridiculous amount of pace. We've already got pace but I wanted to add a little bit more to the squad. It's going to enhance us in the last 19 games of the season."