Ok so lets take 2 people, we will call them David and Terry. (lets assume David and Terry are flat mates or best friends and trust each other fully)
now on the ps3 game sharing (in its semi intended/ tolerated way) works like this:
ps3 1 is Davids he has his account and Terrys account on the console
ps3 2 is Terrys and he has Terrys and Davids account on the console
any accounts on either of the ps3's have access to the content of David and Terry's accounts, so if David buys Battlefield 4 then terry and david can play it at the same time on their ps3's and indeed if John visited David he could play Battlefield 4 on his account on Davids ps3 or Terry's ps3
There terms and conditions in the sony store for ps3 games clearly state and allow this:
Note the last line. Now the ps4 has a different Terms and conditions:
Now the wording suggests that it is now locked to an account and not shareable, however there may be some hope...but youll have to trust the other person very much!
Ps4 1 belongs to David, it has Terry's account set as the primary account but he logs into it using his own account.
Ps4 2 belongs to Terry, it has David's account set as the primary account but he logs into it using his account
Both David and Terry then have access to their own stuff and each others but should John visit he can only use his own stuff and terry's on Ps4 1 or his own stuff and David's on ps4 2
So that leads us to the questions that only people with actual ps4's can answer at the moment:
1) does the above gamesharing method work as theory'd ?
2) what is the advantage of having the system as your home system? ie would David have any issues as his home system is actually Terrys and vice a versa
3) can games be used on 2 ps4's at the same time that are licensed this way (as they can on ps3)?