Until today they offered a plan that let you use their service for free until you reached 50 customers.
Now there's no free plan that you can use after you've launched your site. And for existing apps that use Chargify and have less than 50 customers, they're going to have to start paying $99/month to keep using the service.
Edit: I understand your question now. Yes, the current free plan lets you integrate it into your site, but you can't actually start charging customers until you upgrade to the $99/mo plan.
Now there's no free plan that you can use after you've launched your site. And for existing apps that use Chargify and have less than 50 customers, they're going to have to start paying $99/month to keep using the service.
Edit: I understand your question now. Yes, the current free plan lets you integrate it into your site, but you can't actually start charging customers until you upgrade to the $99/mo plan.