First go here:http://www.darkandlight.net/article.php3?id_article=2396
Then click on the link towards the bottom of the page that says "More about the Master Subscription or Freedom Card"
It seems that there are two account types for Dark and Light. The first being a standard MMO monthly subscription.
The second is an account that's more limited, but has no monthly fee. Instead you get something like credits that you use to unlock restricted areas and equip higher level items. When you repair these items you'll have to use a credit to reequip them. You also can't get certain titles and positions in the world with this account. It seems very limiting, but in essence it's a pay as you go system.
In both cases, you still have to pay an initial cost of around $55 for the game.
Seems like a decent enough idea to me. I could buy the game, play it for as long as I like until my credits run out and not feel like I'm wasting my money by playing it every day of the week. Since my credits stay active for a year since my last login, I can take long breaks. And when I finally run out of credits, well I can ditch my high end gear and become just another mook to participate in the realm vs realm combat.