Let me add a little to what Royster added here about other templates. You mentioned templates for OS Commerce. Having spent years programming with PHP, I can tell you that it will not be easy just taking an OS Commerce template and applying it to OLSB. There is plenty of logic embedded in the templates. Not only that, PHP is in no way supported by OLSB.
Now in defense of those that build applications such as the cart from OLXT (I have not used the cart or seen it in action) and the comments about the security, I can say that the issue is not an SSL enabled connection when adding items to a cart or viewing the cart. The issue is when collecting information from the user such as payment information. In fact, here is a little brief from the BBB Online website:
Use industry standard levels of encryption and authentication for the
transfer or receipt of health care information, social security
numbers, financial transaction information (for example, a credit card
number), or other sensitive information,
The contents of a shopping cart is not senitive information.
Now, if you are accepting credit cards and storing them in your OLSB private site, then you would be in violation and I would be one of the first to point that out. However, keeping information about a cart in a cookie (probably how OLXT does looking at examples of private site) or even adding items to a cart in a private OLSB site would not be a security risk. Then a person can send all items at once to PayPal (Don't know how Google CheckOut works) and the collection of information is secure and meets the needs of the BBB as well.
Also, the OP complains about having a solution providers information on a the website. I'm sorry if it upsets you, but please understand, the creator of that application is offering you an item to use at no charge. In my mind, you should provide all the links that you can back to their site and possibly even donate to their efforts. That's how stuff is made free online.
When you use Firefox, IE, Word or any other program, the name of the product is there and many of those applications are paid for applications. I'm sorry, but if you are going to complain about what developers offer for free, you will see less and less of those items available for your use. We have to make a living as well, but we do like to give stuff away in appreciation, please appreciate those that offer you the free items.
Ted