NASA can probably beat the free market in getting a handful of people to Mars, but for mass colonizition, it will take a market. The government could help with tax incentives and establishing property rights in space, e.g., for precious metals on asteroids.
Repeal the Treaty and open a Land Office. The Land Office will need a budget, but its revenues should more than pay for staff and office furniture.
I have a letter from my Senator that says withdrawal from the Treaty may prove necessary, but it won't happen until the private sector makes enough noise.