PayPal is the payment processor for LAVA however you don't HAVE to have a Paypal membership. At the bottom of the PayPal processing page it gives you the option to use a credit card of your choice. I'm not sure if this is available in all countries.Premium membership is a way to get some additional features, indicate your support to the community and give the contribution a name so accounting can reimburse you. If, after getting a membership, you feel that you want to contribute more, click on the donate button and enter the amount of your choice.
My goal for next year is to get enough funding to support a dedicated server. This will provide more bandwidth and eliminate the downtime that occurs about once a week (server reboot fixes this right now).