It would be better to include links to .arduboy files stored in an "official" repository. (Hopefully, such a repository could be hosted by the Arduboy organisation.)
Sure, but linking to an externally sourced file also runs the very real risk of the file not being there at some point in the future, even if the magazine still is still around.
As for being outdated, it would be accurate to that edition of the magazine. If the game gets updates later on, the mag isn't magically going to describe the new version of the game. I for one, would rather the mag and the copy of the game match, rather than only being able to fine a copy that was updated to 'final' version and nothing like what arduboymag described it as.
As for licencing, surely the permission of the developer would be easy enough to acquire? Maybe even persuade them to create an arduboymag version demo?