Unless there is magic going on with the ABS (assumed ) to be used for the Liberator, I don't think I'd want to be there for the first shot, and certainly for the second shot.
Here ya go, video of it being fired. I believe that was a .380.
As Brian said, if the combustion temp of powder vs the melting point of the components were an issue, there's no go in use today that would be safe. Will the gun eventually wear out? You bet. I can't imagine the rifling (if it even has rifling?) would last too long, and I imagine parts in the action and barrel would eventually warp. But as long as it's over-built enough, I doubt it would catastrophically fail after just one round.
Anyway, this is just a proof of concept. They built a pistol almost completely out of 3D printed plastic (with only a common nail as the only required, additional part, as a firing pin) that fired without failing. That's very impressive. Imagine what we'll see when this process gets more refined and the materials get better.