The license key is a ".qkey" file attached to the purchase receipt email sent to you immediately after your payment clears. Please make sure quadspinner.com is added to your mail whitelist to prevent it from being captured as spam.
The subject line for the email is typically:
[LICENSE] Gaea Professional Edition EAP - ID XXXXXXXXXXXXXXXX
The "XXXXX" is your transaction ID.
Do not share this Transaction ID with anyone except QuadSpinner staff. It is your and your license's primary identity with us.