Pantheon‘s new hosted Drupal service opened to the public today, with prices starting at $100 a month. Pantheon is a startup co-founded by CEO Zack Rosen, a well known Drupal contributor (and a nephew of noted NYU journalism professor Jay Rosen).

Drupal is a popular open source Web content management system. It’s become especially popular with media organizations, and companies ranging from Al Jazeera to Fox News to Mother Jones to The Economist. Perhaps the best known example of a Drupal site, however, is whitehouse.gov.

But it’s seen as something more than just a CMS – some think of it as a full fledged Web development platform, like Ruby on Rails.

This is where Pantheon seems to differ from Acquia, a company founded by Drupal creator Dries Buytaert that offers enterprise Drupal support and hosting. (Neither company had responded to my request for comment by publication time.) Pantheon seems to be targeting developers who want to focus on development rather than maintaining infrastructure and configuring software. It’s more of a platform-as-a-service play. Acquia does offer a service called Dev Cloud, but it includes a wide variety of other services as well.

Update: I spoke with Rosen shortly after posting this. “We love Acuia, and we’ve worked with them in the past,” Rosen says. “But we have a different technology stack and a different set of assumptions.” He says Acquia is mostly in the business of selling enterprise support and managed hosting optimized for Drupal, while Pantheon is focused on creating a fully pre-configured stack for developers. Pantheon’s offering sits somewhere between Acquia’s Drupal Gardens offering, which is a fully hosted Drupal offering but doesn’t offer much room for developers to do customizations, and Acquia’s Dev Cloud, which depends on developers to install and manage their own Drupal instances.

Update 2: Rosen contacted me to say my comparison between Pantheon’s offering and Acquia’s existing offerings is incorrect. He says “In terms of products on the market, it is much more analogous to Salesforce.com as opposed to enterprise software hosting services like Engine Yard, Rackspace managed cloud, and Acquia managed cloud.”

Pantheon has an experienced team, but Acquia has a head start in the market, and has its eyes on an IPO. Pantheon will also face competition from PHP PaaS providers such as AppFog and Engine Yard.

Pantheon is funded by Adam Gross, James Lindenbaum, Kenny Van Zant, Floodgate, Baseline and First Round Capital.

Services Angle

Drupal is one of the most popular CMS systems in the world. As noted above, the White House runs its site on Drupal. Furthermore, it’s an incredibly powerful and flexible system for building sites, and treating it as a development platform and not just a piece of software makes sense. As the competition in PaaS heats up, expect to see more niche services like this.