I believe this is now done through the Adobe Mobile Marketing services where you can use in-app messaging.. including a custom HTML page that you can create to have your user agreement.
This displays according to the trigger events your choose, so you can select first launch for instance.
Will try and find you some links ..
Here is:
See Analytics Mobile Apps in the table in Digital Publishing Solution Help | Analytics for DPS 2015
.. and this is what I was referring to earlier https://marketing.adobe.com/resources/help/en_US/mobile/t_in_app_message.html