They are clear in their terms about not buying email list;
"GetResponse strictly prohibits users from renting, leasing and/or purchasing email addresses from a third party, as well as from gathering them through surreptitious methods, such as scraping or harvesting."
"Importing or in any way using purchased leads with an AWeber account is strictly prohibited.If you paid money or in any way purchased a group of pre-existing leads, these may not be used with AWeber. This includes co-registration services, "safe lists" or any type of free leads given to you. Only people that have specifically requested information directly from you may be emailed through AWeber."