It's not GAAP revenue until the product is out of your hands and in a usable state.
So you can drop the license in an envelope and recognize the revenue immediately, but only if the recipient could have used it if they'd grabbed it from the mailbox.
If the license isn't usable for another month, you can send it to the customer, they can pay for it, and you can even spend the cash, but the payment sits on your balance sheet as a liability until the moment the license becomes valid.
And as with anything, sufficiently motivated legal representation will argue your way into the most favorable grey area possible. Arbitrary example being a license key that activates the software, but the activated software is effectively a hardcoded trade show demo version. The point most folks seem to be making is that “this isn’t corporate america’s first rodeo” and that like many other industries before software will end up with it’s own numerous nuances and loopholes established by extensive litigation.
So you can drop the license in an envelope and recognize the revenue immediately, but only if the recipient could have used it if they'd grabbed it from the mailbox.
If the license isn't usable for another month, you can send it to the customer, they can pay for it, and you can even spend the cash, but the payment sits on your balance sheet as a liability until the moment the license becomes valid.