Here is how I understand it.
Yes, you can join ADC as a student for free. Actually, anyone can join for free. However, you do have to have a paid membership to be able to purchase your one piece of hardware at the student developer discount price.
Therefore, if you haven't paid your student membership fee of $99, when you go to the ADC hardware store (looks just like the regular online apple store, except cheaper!
) and you select your Mac, it will kindly add the $99 membership fee on for you.
Note that they require you to fax in a copy of your photo ID/student ID and proof of current enrollment at your school before you can actually make the purchase.
At least that's how it looks
like it works, to me...