Facepunch Studios has released the s&box code to the public, but there are some caveats
s&box is both a platform for launching UGC (User-Generated Content) games and a set of development tools from the creators of Garry’s Mod. Recently, Facepunch Studios decided to make the project open-source and published its source code on GitHub.
s&box
It’s important to note: s&box is built on the Source 2 engine, but components owned by Valve have not been included in the GitHub repository. The developers shared what they wrote themselves in C#.
Facepunch Studios mentioned that they were partially inspired by the example of Godot — another open-source engine — to publish s&box’s code. The studio is convinced that the gaming industry needs more tools like this. That is why they decided to distribute the source code under the permissive MIT license, allowing anyone interested to experiment with the code and even create their own engines.
“From a business perspective, it might seem strange to develop an engine and release it for free, without royalties, and also make the code publicly available. But we are a bunch of geeks who love what we create. We want everyone to use it as they wish, we want to provide opportunities,” explained Facepunch Studios.
You can review the s&box source code here.