In some ways, Acquia has turned the usual development model for software-as-a-service upside down. Established vendors such as Salesforce.com began with a core product and then offered a platform for customers and partners to add new capabilities. Because Drupal is open source, its developer community has already developed dozens of add-on modules that can now be bundled with Drupal Gardens, Buytaert said.

The hosted service will be free throughout 2010, after which Acquia will offer a basic service free and two subscription services with more advanced features. The prices will be US$19.95 and $39.95 per Web site per month, according to the Drupal Gardens Web site.

The subscription services will be aimed at businesses that want to set up "micro sites" to manage projects, conferences and campaigns, Buytaert said. If companies want to stop using the service, they will be able to download the source code for the Drupal Gardens CMS platform and run it in-house, he said.