Google on Monday launched the Google Apps Referral Program in the US and Canada. The referral program lets you share Google Apps with other businesses, and pocket a $15 bonus for each new user that signs up. Here’s the fine print: You can refer an unlimited number of customers. You’re rewarded for each referral customer’s first 100 users. A user is an individual account belonging to the customer domain. Your referral amount will be based on the number of users who have paid for at least 120 days. To participate, you’ll need to provide your name, email address, a valid taxpayer ID number, and a bank account to receive direct deposits. Google says many of its existing customers learned about Google Apps for business from their own customers, friends, as well as networks, and the company just wants to “help continue the momentum.”