Gitmask lets you hide the true origin of code, which can be useful for a variety of reasons.

Github's tagline is social coding. Unfortunately that means that every commit you ever make is visible to everyone. Every commit.

Simple

Adding a new git remote is much easier than setting up another GitHub account and remembering to use that secondary SSH key.

Mystery

Bitcoin is fairly mainstream now, but its inventor is still a mystery. Sometimes it's better to let the code speak for itself.