IPad – Use Airplay Mirroring and Airplay Speakers at the same time on iPhone

No - Apple TV (currently) engages HDCP only when needed to protect content that requires HDCP. This is called out in the specifications page as a footnote in teeny tiny grey text:

• Requires HDCP when playing protected content.

You should be able to use whatever HDMI recorder you please as long as the software doesn't detect protected content being played. You can be sure the engineers have considered that they need to pass the HDCP status from say Hulu or rented movies on iOS to the Apple TV when playing protected content. So if you want to record a demo of your normal app usage, this will work well, but not so much for bypassing HDCP by indirection.

If you can gat a computer, a much more robust recording solution is offered in XAleXOwnZX's answer.

This is a bug in 10.8.

To be more precise: after using AirPlay Mirroring in one account, one needs to log out that account before one can use Mirroring in another account on that same Mac. The same applies if you happen to use Mirroring in the guest account first, and then leave that account logged in and try to use Mirroring in some regular account.

Also, any text you might recognize is not from the current screen of the other account, but from the last Mirroring session of that account. The current screen might already not show that text anymore.

(It's fine to log in again right after logging out; apparently some cleaning up is done when logging out. I've reported it, but unfortunately used Apple's feedback form, rather than the developer Bug Reporting. Hence, I cannot see the status of my report. I will delete all this if it's fixed in some future version.)