My employer Acquia is a commercial open source company. That means that they make money (commercial) off of software they don't own (open source) and there are more than one of us (company). It should be clear then that Acquia's survival is totally dependent on the success of the software it provides services around, Drupal.
Drupal has been doing exceptionally well as of late. In fact, Acquia just relased "the showcase"; it is a website detailing over 1000 high profile Drupal sites. To name drop a few, The Whitehouse, Amnesty International, NCAA, The Economist, www.jacobsingh.name, and many, many more. Drupal is charchterized by having a very robust community of thousands of developers, rapid innovation, successful conferences, local community organizing and a thriving ecosystem of service providers.
The main thing threatening Drupal's growth right now is a lack of expert Drupal talent to meet the demand. We now compete with the very largest proprietary systems and software companies in all industries. We have the tech, it's proven, but we need enough people to execute.