It sounds like you're asking about license restrictions. Each project has a license associated with it. Those licenses dictate how projects can be used and what sort of requirements they have for being included in other projects. There is no standard license for projects uploaded to GitHub. You will need to check the license of each project you use to see if you can use and distribute it in your own project.
Here is an overview of the most common licenses and what they mean.
Hope this helps!
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