I am a linux user and have been able to write not-too-complex C programs. I have also used makefiles. I have tried to download tablebase generator programs from GitHub but do not understand how to do this. The site seems to be primarily for programmers rather than users. I'm also not sure whether downloading source code costs money there.
First of all, everything on Github can be downloaded freely. Normally, there should be a download button somewhere. Do you have a specific project in mind sou want to download? There seem to be several tablebase generators available. One is available from https://github.com/syzygy1/tb it seems to have decent documentation. There is a green button on the top right labeled "Clone or download", which allows you to download the whole thing as a zip file. From there you will have to follow the provided instructions to compile it. For questions on this another, more programming-related SE, may be more appropriate.