Tesla was incorporated in 2003 by Martin Eberhard and Marc Tarpenning. Musk did not register the company, but he led and largely funded its 2004 Series A, served as chairman, and was the controlling investor. A 2009 legal settlement formally entitles five people — Eberhard, Tarpenning, Musk, JB Straubel and Ian Wright — to call themselves Tesla co-founders. So "he just bought in" is misleading: he is, legally and by agreement, a co-founder.