Yes you can publish your game with your free asset.
What is not allowed is reselling of asset in a standalone version, for example you purchase a free tree pack on fab and then make a commercial product which contains only that tree pack.
Also make sure these free assets don’t have copyright issues or stolen assets.
If there are asset mark as NoAI, your software can’t be part of generative ai features.
More detail Source: https://www.fab.com/eula