As per the laws of my country, in the case of software, I can register only the code it looks like*. In this case, record in the sense of having it in writing: this person was the author of the game, 
How can I have access to this entire source code? Just for register purposes, as I made a game for a “sponsor/supporter”, and he liked it so much that he offered to register 
(and he wants to register, and so do I)
The project file is your “true” source code. But what they probably want is the exported source that has been converted to javascript or html5.
Export your game manually and choose either desktop or html5 exports, select a folder, and then that folder will contain your exported JS/html5 code.
Hmm… Thanks for the reply 
In this case, does the web game only use HTML5 and JavaScript, or does it use another language?
Exported games source code will be javascript and html5 only, regardless of whether it is web, desktop, or mobile exports.
I understood! Thank you very much, really. So, I imagine that for mobile, the game+browser is packaged through hybridization, would that be it?
Wait, so GDevelop 5 don’t use CSS for the graphic part?
Sort of, but not quite. It’s packaged using Electron and Cordova. Electron is Chromium. The code sremains the same.
Not sure what you mean, but no. GDevelop’s renderer is PixiJS for 2D, and ThreeJS for 3D. There’s generally no CSS in any component.
Oh, thank you very much! I didn’t know these things, I learned something new. I thank