[whpalmer4]

I don't know the details of the App store licensing scheme; it may not be possible. I was thinking about the Mac end of things when I said no additional license should be needed, and didn't consider the possibility that your phones might be linked to different accounts and not already have the application on both. If you are stuck buying another license, better that you have to buy an extra iPhone app license than an extra desktop license, given the relative prices!

Yes, he would just use your MobileMe username and password to set this up. I do not believe (but cannot promise) that this should affect anything else on the phone, as it is an OmniFocus setting, not a phone-wide setting. It's a reasonable question, as on the Mac, it does use the system-wide setting for MobileMe username and password.