So far I haven't had to use GitHub.
I've done a LOT of computing for a LONG time. The code for my startup runs fine. I Want to do a few, easy late tweaks before going live.
I have the first server running and am doing a few last little things.
The code is 100,000 lines of typing, 24,000 programming language statements, nearly all in Microsoft's Visual Basic .NET.
The next major step is to gather a lot of data for my database, much more than the data I have for testing now.
I taught computing at Georgetown and Ohio State, published in artificial intelligence and more in computer science and applied math at IBM's Watson lab, and cooked up some maybe new algorithms for my startup.
But I've never needed to use GitHub! I'm not against it, but so far the computing unique to my project has been fast, fun, and easy for me. The main bottleneck has been poor documentation. Then my development computer got sick, then I got sick, but now both I and my computers are all healthy!
The times I tried GitHub, it said that my Web browser is out of date! I have the latest from Firefox and was using my HP laptop with Windows 10 64 bit Home Edition -- what came with the laptop I got just to have something to order parts and gather information for my first server after my development computer quit -- some motherboard data corruption problem.
My server is an Asus old BIOS style motherboard with an AMD FX-8350 processor, 8 cores with standard clock at 4.0 GHz, 16 GB of DDR3 ECC main memory, 7 TB of hard disk, and Windows 7 64 bit Professional. If my startup gets traffic enough to keep that server busy, then I'll have a nice step up!
Especially since I'm using Microsoft, I'll likely use GitHub eventually.