The engine and most of the art here are other people's, used under licences that require saying so. This page is that.
Intersect's asset pack is free to use commercially, which is a statement about cost and permission, not an attribution waiver. Every tile in the screenshots on this site was drawn by the artists named below and is licensed CC BY 4.0.
Client MIT, Editor and Server GPLv3. freemmorpgmaker.com
Licensed CC BY 4.0. Every tile you see in the screenshots on this site is their work.
Generated procedurally at 32×32 to match the tileset palette. Free to reuse.
Intersect's client is MIT; its editor and server are GPLv3. The community graphics pack is CC BY 4.0. Sound effects in the pack are CC0; most item icons are CC BY-SA 3.0; music, where used, is CC BY 4.0 and credited to its composer by name and in the format they ask for.
If you think something here is credited wrongly, that is a bug — say so and it gets fixed.