Like it or not, Impact is now associated with image macros and memes throughout the web. As the Impact font itself is not free to distribute, I was wondering if there were similar fonts available under more permissive licenses? I haven't been able to find one that felt right enough.
It's not the same design, but League Gothic is a good free bold grotesque sans that may give you the feel you want.
Vernon Adams has a very nice alternative, named Anton: https://www.google.com/fonts/specimen/Anton
As he said in other page: "see Google's PR for the Chromebook notebooks that used Anton, big and bright".
The best alternative I know of, that is free for commercial use is Bebas Neue.
Oswald is a good alternative too:
It is worth noting, that although it's still under copyright by Microsoft, it is still available for free (free beer, not free speech) in the Ubuntu non-free repository in the package
sudo apt-get install ttf-mscorefonts-installer
After which it will be available in any Linux applications