Cesium Guidelines

Am I allowed to have my users sign up for individual free Cesium accounts to play my game?

By the way, this game will be free to play without any microtransactions or revenue sources.

The Terms of Service have the final say, and I’m definitely not qualified to give legal advice. But I would say there’s nothing wrong with you asking your users to create Cesium ion accounts. And as long as your users are using Cesium ion for non-commercial purposes, which it sounds like they will be, then there should be no problem there, either.