Monetization in a facebook app for websites

I have a gaming website which also has a facebook app for connecting through facebook.

I have offers and virtual currency for purchase, not with FB credits.

When the app is opened from facebook, it's connecting to the site but shows it in a canvas, as an ifram in Facebook.

I read that it is not allowed to monetize in facebook.com with anything other than FB credits, but i see sites like zoosk.com that have the same problem, but keep the monetization as it is, and you can buy things from them, while in the canvas/iframe.

Did zoosk.com break the FB law, or is there any workaround that they implemented so it'll work.

Also, Gameduell.com redirects immediately to their site when openning the app. it does not appear in the canvas. I read this is against the rules too. is it because it is opened in a new tab?

There are a few questions here, I'll try to address them all separately.

• The rules around monetization and FB Credits are (for now) different for games and non-game apps, so Zoosk is not a useful point of comparison for you.
• Currently it's possible to send a user to a separate site, but this is changing soon (see http://developers.facebook.com/blog/post/2012/08/29/platform-updates--operation-developer-love/ and https://developers.facebook.com/roadmap/#december-2012) - starting Dec. 5, not only are you no longer allowed to promote alternative (off-site) payment options from within FB, you won't even be allowed to use the same app ID for the game displayed on & off FB. So, you should probably consider offering FB credits as an option in the future, and in the meantime you might want to make a concerted effort to ensure your users are aware of the other payment options.
• I'm not 100% sure on the latest rules w/ redirects like you say GameDuell uses, you'll have to research that more if you're unsure. I'd just add that unexpected redirects are harmful to the user experience, but only you can decide if doing it makes sense for your case.