Austen Heller is a wealthy social activist who seems—the first time we meet him—like he's just another Toohey follower. But there's actually a lot more to Heller than meets the eye. For one thing, Heller turns out to have fabulous taste in building design.
In fact, he takes a shot on Roark very early in Roark's career and hires Roark to build him a house. The Heller house becomes Roark's first big solo project, and it has a lot in common, design-wise, with Fallingwater, a famous house designed by Frank Lloyd Wright. Fallingwater was built in harmony with a nearby waterfall, and Heller's house is built in harmony with the surrounding granite cliffs. Heller becomes a good friend of Roark's and tries to defend him against society.
Heller straddles the worlds of both Toohey and Roark. He attends one of Toohey's rallys, but his speech to the workers is super Roarkian in tone:
"There is no conceivable law by which a man can be forced to work on any terms except those he chooses to see." (1.9.47)
Heller goes on to speak of "freedom to agree or disagree" in his speech regarding people's right to strike. In a way this is a totally pro-Roark sentiment; Heller seems to be a fan of individual action and people's right to exercise their freedom in the form of strikes. Really, Roark is also on a sort of strike against society in his refusal to bow down to it, and Dominique also strikes against the world during her campaign-against-happiness era.
So Heller turns out to be aligned with the novel's heroes: he's a progressive guy who actually supports individual freedoms, unlike Toohey who uses progressive ideas to suppress freedom.