As of now, Steam Greenlight will allow developers to submit non-game software to the burgeoning platform.
Steam has approved dozens of applications from developers for games, but now non-game software will be catered for by the service.
According to the Steam blog post, the update adds "the ability for developers to post non-gaming software for consideration by the Community." The process of voting and approval will work exactly the same as it does for games.
Submission details here.