A gift giving program is a pyramid scheme dressed up like something that is philanthropic. Whether it is legal depends on how it is different from a pyramid scheme.
The answer to this question is yes, however there are some states that are really scrutinizing these real estate transactions and looking at them as potentially fraudulent and possibly can be considered mortgage fraud. Georgia is one of these states. As long as the down payment is truly a gift and not some sort of sham, then it is legal.