Copy games from friends ps4 to your own ps4

Solution 1:

To my surprise it's possible! But it will completely erase what you already have on your PS4:

When you transfer data, all data saved on your new PS4™ system is deleted

Exact steps are the following:

1. Connect your new PS4™ system and your current PS4™ system to the same network.
2. On your new PS4™ system, sign in to PlayStation™Network. If an update file containing the latest version of the system software is available, a screen appears to guide you through the update process. Follow the on-screen instructions to perform the update.
3. Connect your current PS4™ system directly to your new PS4™ system with a LAN cable.
4. On your new PS4™ system, select (Settings) > [System] > [Transfer Data from Another PS4]. Follow the on-screen instructions.

So, you can move all your friend's stuff to your PS4, then add your own account again and use your own account to access all moved games. Your friends saves will be accessible only for his account.

If you decide to take this route, don't forget to backup your saves / screenshots / videos / whatever else you have to usb.

Source: Transfer Data from Another PS4.