Yes, it's an important point that SQLite is not a project with an open contribution model. However, they do presumably accept external contributions in the form of bug reports, suggested patches, etc. etc.
>>foldr+(OP)
Another cool project from Dr. Hipp is the fossil SCM, which SQLite is developed in, and one of it's features is that it ships with a web view similar to GitHub. The website is actually the web view of the repo. (Apologies for expressing that in a confusing way, I knew it was on the website, I was referring to the website as the repository.)