All who wish to enter need a room key and at least one member of group should bring DVC member ID. The Cast Member working the desk does not always ask for the member ID but better to be prepared. If he/she insists on seeing it and you don't have it, you'll have to run back to the room to get it before being allowed up.
If you are staying on a friend's points without the friend and are not a member yourself then you won't be allowed up. The DVC member needs to be with you to go up.
If you are staying on a friend's points without the friend and are not a member yourself then you won't be allowed up. The DVC member needs to be with you to go up.
Actually the official policy is that any individual staying on points--member or non-member--is permitted to use the lounge. Room keys used to have "DVC Member" clearly printed on them and that was apparently sufficient.
Since the DVC Member notation was removed from room keys, some CMs apparently have taken it a step further and asked to see a member ID card. But really membership is not required to access the lounge.
Post #6 in this thread quotes the written policy from DVCMember.com: