That's a very important point if you're distributing your software to non-technical users, but a download button in either the README.md should do the job. You could also use a GitHub site and host a simple download site for your repo.

It seems to me that if a project on GitHub is interested in making it easy for lay-people to download, then a little dose of

   https://pages.github.com/

should do the trick? (Personally I found SF's interface confusing and incredibly "busy" -- I don't think lay-people would fare much better, but I could be wrong.)

There's no big "Download" button but you can easily add one yourself.