Offhand, we're only aware of the WordPress-based membership plugins listed on that help page. Both of those use our standard custom/third-party Integration method to receive order notifications from our system:
http://www.e-junkie.com/ej/help.integration.htm
If you can find another, non-WordPress membership solution that supports PayPal IPN for order notifications, they may be able to support our IPN-style Integration method with little or no modification -- we'd suggest contacting them with the link I provided above, to inquire whether they can work with that.
If you'd like some more direct assistance with finding such a solution and setting that up, we can recommend the competent, E-junkie-experienced developers listed at the Developer Directory link at the top of our site.