They haven't open sourced the game itself yet. They made the announcement back in April on their own site.

I remember seeing an article about it a month back. It's just the backend that they're open sourcing, since that will let it be audited for bugs, help the community make mods for private servers, and help other studios in the future since the backend is the hard part about making MMO's. The devs are wanting to maintain ownership of assets like art and writing so those will not be oprn source

IIRC only code, not asset files.

What does it use now??

Judging by the fact that I have never heard of the game or the company before, I guess it's tiny and obscure, meaning it would have either been completely ignored by hackers or some hacker would completely flatten it with hacks.

Probably nothing about that has hanged by open sourcing it.

Probably, and that's the point, since said exploits can be then publicly acknowledged and patched.

Security through obscurity is generally considered terrible practice in the cybersec community. It's much better to actually find and fix the flaws than just put your head in the sand and hope no one notices the issues.

Exploits in games and the exploits used by hackers for various other purposes are very similar in nature if less often in effect.