Actually, CubeCart will work with Mal's. There is a direct hookup. I use Mal's all the time with certain applications, have about 6 or 8 accounts with them. But you have to understand that it's not free if you want to process cards online.
The free version of Mal's only collects the card information on his server. You then have to login and enter a seperate password to get to the secure area to retrieve the card info. You still need to have some sort of merchant account to hand enter the data you get from Mal's. So you still have the monthly fess for a card processing account from Moneybokers or whoever.
Mal's will do the hookup to your gateway or processor, eliminating the need to login and hand enter the data, but there is a charge of $ 8 a month - on top of the fee you are paying for your gateway / processing. So it is more expensive than it first apperas.
And all you can do with Mal's is use Buy Now buttons. It's not a big deal if you are selling a few items from a regular website, but it has no "shopping cart structure" as they re generally thought of. There is no template of any sort, no design, no category / sub-category breakdowns, etc. If you are quilting at home and hve 4 sizes and 6 designs and have a page for each with a Mal's Buy Now button, it's great. But if you are selling 100 or more items it leaves much to be desired.
As I said, I use it. Most of my hosting sales pages go through Mal's, but they have less than 10 items to offer. And Mal's does have a free affiliate program, plus it ties into other affiliate packages, which is why I use it for the hosting.
I have other "retail" type shops with thousands of items that I port to Mal's for the money. But the sites are designed as shopping cart tyeps with templates, categories, etc. Just the actual sales are in Mal's, everything else is in the cart. Same with CubeCart. You can have a complete CubeCart site and when a purchase is made the sale goes to Mal's, but the cart the customer sees is all CubeCart, just the payment page is Mal's.
As I said, I use Mal's all the time. But I'd never attempt to use it from the ground up as a cart. There is no structure to it at all, just buttons.