I initially had some trouble when I tried to purchase a deal by logging into my SourceForge account. I was perturbed at the idea of needing a second/separate SourceForge account to make the purchase.
Then app103 pointed out to me that it's a StackSocial
store, and all the deals found there can be found at any site that has a StackSocial storefront. Suddenly things are making a lot more sense.