I have uncopylocked three of my projects that I believe new and experienced scripters alike can learn from. I encourage you to read through code that you want to understand in order to build a stronger foundation. If you need help understanding something, you are welcome to message me here on the DevForum. 
None of these projects are completely finished, but all have a worthy codebase to learn from. I will explain each project below, along with what you should ignore when looking at it (deprecations from when it was made). I have no intention to do anything with these projects, but if you would like to you can!
With this, and any other open source project you learn from- please use it as a starting place. By no means do I claim that any of this code is heavily optimized or immediately production quality. Use these to learn concepts, but cross-reference it with the Luau Reference Manual / other DevForum resources & tutorials.
RoQuake
open-sourced place: click here
RoQuake is inspired by bhop & quake. It creates custom movement physics that depend on player skill for successful navigation. By moving your mouse & practicing you will land easier and gain more speed.
Gameplay:
- Intense amount of deprecations likely (wrote in 2017)
- I don’t recommend making a viewmodel how this project does.
- Prone to not work 100% of the time that you load in- I never debugged why because I left the project behind.
Velocity Vehicles
open-sourced place: click here
Velocity Vehicles was made this week as something to tack on top of this post. It uses a single part & BodyMovers to create a functional and versatile vehicle. Lots of room for improvements and features inside Vehicle constructor. (also note that BodyMovers are no longer preferred to Roblox’s new physics movement objects, which this game also uses).
Gameplay:
- Vehicle class module is very messy and has TODO statements left.
- Game uses BodyMovers, again, these are no longer preferred.
Perlin Noise Terrain
open-sourced place: click here
This showcase uses very basic noise to generate terrain. It is not very versatile but uses math.noise. I do not recommend using this project’s source inside your own games- I recommend learning from it and writing your own terrain generation (because this place’s hierarchy makes no sense at all, it is from 2016-2017).
Example:
- Hierarchy makes no sense, not recommend to re-use source code outside of the noise loop.
Again, to reiterate, please cross reference any open-source project you learn from with a language’s modern documentation to find deprecations or better ways to handle your code. Almost all of this code I would not put inside of a game that I write today, and it is primarily expected to be used proportionally to what concepts you are interested in learning. Hopefully this helps someone.