I don't know. Carmack doesn't strike me as the sort of person that would want to waste his time with all the extraneous details involved in starting a company. Seems that he prefers to have his own isolated fief where others can handle the sales side while he can focus purely on R&D where he excels. He probably did some calculation regarding the potential of the technology vs. the competence of the founders and decided it was an important enough problem that he would be happy working at for the next few years.
Before his help, I'm not sure it was more than an interesting demo of technologies we'd seen before.