There are a number of them like git and bitcoin which start out with one guy building a novel algorithm and then releasing the source to the world afterwards.

There are a number of them like git and bitcoin which start out with one guy building a novel algorithm and then releasing the source to the world afterwards. The definition of open source might include such a thing, but a project that originates from a lone genius rather than a community is not what is usually meant when people speak of open source.