I love the weekly free downloads from Amazon, and this is a particularly good one. I've found some good music, and I order albums from Amazon frequently enough as a result.
This particular offering worked fine for me. I did NOT have to submit a CC to make the download, but Amazon's already got my data in their servers.
Having said that, two 'FREE' downloads last week ended up being billed at their sale price, about $5 total. I emailed Amazon customer support and they DID promptly take off the charges, so no harm done.
BUT... check your receipt when it comes in. Anything can happen!