Do I really need a SSL certificate to make the module work?
An SSL certificate is indeed mandatory nowadays, as a good share of Facebook users have been migrated to secure browsing and forces all content on Facebook to be SSL / https compatible. You can of course make the Shop Tab work only on he http mode instead of https, but it will only be visible by users who have turned off secure browsing in their Facebook preferences.
If you are hosted on a dedicated server or VPS, you can purchase an adequate SSL certificate at a low price on http://www.sslcertificate.com/brand/ssl-cert-geotrust/rapidssl.html for only $13 per year, or about $1 per month.
If you are on a shared hosting plan, you need to check with your web host, but it is 100% compatible with shared SSL certificates provided by major web hosts such as OVH and 1&1.
If you are hosted on a plan that does not offer SSL, we encourage you to switch to OVH, or better yet to www.772424.com. They are one of our partners and provide you with a high-end hosting service and excellent customer service. A few sites hosted with them: www.blog-ecommerce.com, www.paytvcard.ch/shop. Clients having migrated there are enchanted, with a faster website and no more problems caused by server limitations. Of course, 39€ / month is a price to consider, but a quality hosting plan has a direct impact on your Google rankings (Google favors fast websites) as well as your customers and sales (visitors run away from slow websites and go shop somewhere else). It therefore represents a real return on investment.