Their site’s front page says this:
Join a community of over 227,000 players and creators!
Build and explore unique worlds, customize your character, socialize with others, and design your own creations. On Polytoria, the only limit is your imagination. Jump in and join the adventure today!
Play unique places made by the community.
Play online places made by thousands of players like you. With so many places to choose from, you’re sure to find something you’ll love.
Create anything you can imagine.
Create your own places with our clean, easy to use workshop. The extensive Lua scripting language and the simple APIs give you the power to create any place you want. With Polytoria, the place is yours.
Connect with other players.
The Polytoria community is a great place to meet new friends and learn from experienced developers. Connect with other people on the forums, in chat, or at one of our many events.
Also, they seem to be going open source under the MPL-2.0 license once Polytoria 2.0 releases.
Just tried it, seems pretty ok, everyone’s complaining about the servers and rightfully so, but its fun and reminds me of roblox in the past a bit.