Why does the beginning of `git log` for the Bitcoin source on github say 'sirius-m' was the first committer?
The source code was originally hosted in a rar file on Bitcoin.org. It did not use any Source Control Management. Later, when more people began working on it, one of the earliest developers, Sirius, moved everything to SVN on Sourceforge. That was later moved to the current Github repository and switched to using Git.