So you have 5 groups
1) Subscribers - They have paid money and get access for the length of their subscription
2) Mag Buyers - They get access every month they buy the mag. All they have to do is enter that months code. They have paid money for the mag and get a free months access with it. This is reusable for every month.
3) You are a God or Mod or SuperHero or Hero - You are at the top anyway so you get access free
4) You dont buy the mag - so there is a $20 year charge for something that is based around a magazine and is a commercial entity. Heck slashdots subsribtion cost money. You need to stay afloat
5) You dont buy the mag and dont want to pay so you just lurk