If someone wants to see all of the albums in your Forever™ Account that you have set to Friends & Family and Public then yes they will have to join Forever™, and you will need to add them to your Friends & Family.
Once they join Forever you can then search their name in your “Friends & Family” section and click on “Add to Friends & Family” when you locate their account. You can also “Invite” people to Forever and to be part of your Friends & Family. You can also do this within your Friends & Family section, by clicking on “Invite Friends” in the upper left hand corner.
If you just wish to share an album that you have set as Public, you can just create a share link for that album and then you can share it via email, Facebook or just sending the link for the album. Since the album would be set as Public then anyone with that link could view it, even if they are not a Forever member.