Reallly you have no option but to take the tours unless you hire a car which I would recommend if there's more than 2 of you as the walks are well signed and the tours are very expensive.
Maruku is a not-for-profit art & craft organisation, 100% owned and controlled by Anangu (Aboriginal People from the southeast and west of central Australia). Maruku was established in 1984 by and for Aboriginal people through the trading arm of Anangu Uwankaraku Punu Aboriginal Corporation. Anangu created the corporation mainly in response to a growing need for the effective co-ordination of Marketing and support services for Aboriginal craftspeople living in the region. Maruku literally means “belonging to black”.