Hi,
The eWay payment plugin is a plugin where the user put his credit card information directly in your website.
So with eWay, a SSL certificate would be required for your website.
Otherwise, some critical information could transit between your customer and your server without any encryption security which is not a good thing.
Some payment plugin redirect the customer to the payment plateform (like paypal), the website do not require a SSL because it does not receive any critical information.
If you use a payment system where your website receive the credit card data, you have to secure your website/server/domain with SSL.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.