This is a small release to fix up some issues in r51. Most importantly, Construct 2 was incorrectly rejecting some people's licenses. This should now be fixed, but do let us know if you still have any problems. There's one more attempted fix for the issues some users have had with the layout view not rendering on Radeon graphics cards. (That one's been driving me mad lately!)
In case you missed it, r51 had a lot of changes, fixes and additions - you can find the changelog for it on the left.