Downloading FREE royalty free models. Can I use them for personal use and then make a devlog YouTube video showing my game project with those models in it?

You can use free models for personal use without problems, although that model that you showed as example should be under editorial license since it contain logos of xbox and halo game.

This is what I found in for the "royalty-free" license agreement section for using the models in-game:-

21.2. The Buyer’s license to Product in this paragraph is strictly limited to Incorporated Product. Any use or republication, including sale or distribution of Product that is not Incorporated Product is strictly prohibited. For illustration, approved distribution or use of Product as Incorporated Product includes, but is not limited to:

- as rendered still images or moving images; resold as part of a feature film, broadcast, or stock photography;

- as purchased by a game’s creators as part of a game if the Product is contained inside a proprietary format and displays inside the game during play, but not for users to re-package as goods distributed or sold inside a virtual world;

- as Product published within a book, poster, t-shirt or other item;

- as part of a physical object such as a toy, doll, or model.

21.3. If you use any Product in software products (such as video games, simulations, or VR-worlds) you must take all reasonable measures to prevent the end user from gaining access to the Product. Methods of safeguarding the Product include but are not limited to:

- using a proprietary disc format such as Xbox 360, Playstation 3, etc.;

- using a proprietary Product format;

- using a proprietary and/or password-protected database or resource file that stores the Product data;

- encrypting the Product data.

Hi there,

Products sold with Royalty Free Licenses can be used for commercial purposes with no additional liabilities, extra royalties or other license fees applied for multiple usage of the product and volume of the end product (e.g. video game, film, animation, VR/AR application, visualization, etc.) created using the product. Even if they're free. Products published on CGTrader may not be sold, given, or assigned to any other person or entity in the form it is downloaded from the site.

If you buy a product and use it as part of a physical object such as a toy, doll, or model, you can distribute it. However, as mentioned before, product cannot be sold in the form it is downloaded from the site.

If you have any questions, please contact us via support@cgtrader.com.

Kindly,
Greta from CGTrader

So if I print a helmet file and prepare it to cast it! Can I sell the castings?