SD is the same as USB, if you want to certify your product as "SD
card/USB 2.0 compatible" or use the official logo on your product you
have to join the "association". You do not need to join the association
just to sell a product using the card.
They are rather naughty about this on the SD association website. In
their FAQ http://www.sdcard.org/developers/faq/#licenseforhosts:
Q: Does my company need to obtain a license to sell a product that hosts
the SD card?
A: Yes, the license required to use the logo is the HALA license.
Which doesn't answer the question at all. The answer is "No, unless you
want to use the logo."
--
Tim Mitchell