It's a "popular" anti-cheat integration system that is widely known for performance issues. I'd recommend SEGA not bother with it. But I'd also recommend SEGA to dump GameGuard as well, in favor of developing something in-house. The reason being, I know a fair few people who want to play Phantasy Star Online 2 on Linux via Proton/WINE, but GameGuard disallows that.
Converse with fellow players