GearUP Booster is a game network accelerator, not a VPN for general browsing. It routes traffic for supported games so the connection can take a shorter path, which is meant to lower latency during play. GearUP describes the supported games and platforms on its own site.
The desktop app covers the PCs, consoles, and phones GearUP lists for each title. Subscription length, and which games are included, depend on the plan bought from GearUP. A percent-off deal on this page is GearUP’s own discount, separate from KPON cashback. A game that is not on that plan’s list is not accelerated.
Where this page shows an Up to cashback rate, that rebate is from KPON, not from GearUP, and it follows the terms above.