I clicked the link again and now it looks different.
It looks like that you go there once you are in a Framily to fill out the form to get the gift card, etc.
It says this:
Welcome to the Framily!
For a limited time, when you join an existing Sprint FramilySM Plan by bringing (porting) your number to Sprint from another carrier, you can register to receive a $200 Visa® Prepaid Card. Plus, get up to $300 with the Sprint Buyback Program!*
Here's how it works:
This offer is non-transferable. You must have joined Sprint on a Framily ID from a referring Sprint Framily customer.
Complete a registration for each new line of service ported to Sprint.
For more information, please review the offer's Terms & Conditions
Remember: All lines must be ported from an active wireless line at another carrier and remain active on a Framily Plan for 31 days to receive the prepaid card.
*Buyback can be executed at store at time of purchase or later online.
Mav.