To provide additional benefits for users of Object Desktop and other Stardock products, we have set the site up to allow you to easily connect your WinCustomize account to your Stardock customer account. Connecting your account will provide you with (currently) unlimited downloads. In the future, we hope to be able to provide Stardock customers with additional benefits.
There is no current cap on # of downloads for users who have purchased Object Desktop or WindowBlinds or any other Stardock product. If you want to subscribe to WinCustomize to get access to the WinCustomize browser, the upcoming premium skin suites, text ads, and more, by all means do so but you don't have to subscribe to download skins.
Hope that clears things up.