Apple iPad 2 power adaptor issue

I built a wonderful Pong Clock v 5.1, Oct 2013 by Nick Hall.

I use my Apple iPad 2 power adaptor to hook up to Arduino Uno R3 to run 2 - 24X16 Sure Electronic 3mm boards.

Will the power from Apple damage Arduino Uno board?

I check on Arduino board to make sure it is cool. Yes, it is.

What do you think?

By the way, the Apple power state 5.1 volts and 2.1 AMP - 10 Watts.

I use one.