Salesforce.com has signed an agreement to acquire the Ruby platform Heroku for $212 million. The deal has been approved by the Heroku board and is expected close by Jan. 31.

Ruby is an open source scripting language that originated in Japan and became popular for Web and frequently changing business applications. Its adherents often use a rapid-coding environment known as Ruby on Rails. Many leading Web applications are built in it, including Twitter, the flight delay predicting site Flightcaster, and the video download site Hulu.

Salesforce CEO Marc Benioff didn't hesitate to invoke those names Wednesday as he announced the deal on the second day of the Dreamforce Salesforce.com user group meeting in San Francisco. It sounded as if, overnight, Salesforce.com had gone from a proprietary platform as a service, offering only Apex, to one that supports a dynamic and popular open source language.

"We've been somewhat myopic. Customers have been telling us, 'You're too proprietary. You need to open up.' It started to get to me," Benioff declared at the start of his second keynote address in two days.

"We want to add Ruby, Ruby on Rails," he added. Salesforce's own new service, Database.com, was written in Ruby, he noted. There are an estimated one million Ruby programmers currently, with the number expected to expand to four million over the next few years. That compares to the six million existing Java programmers.

At the same time, Benioff left open a major ambiguity. It sounded as if thousands of Ruby programmers will soon be flocking to the Force.com platform as a service, but Heroku is primarily a front-end system for Ruby programmers. It takes applications and deploys them to its own multi-tenant environment --- built atop Amazon Web Services EC2. In acquiring Heroku, Salesforce will be feeding, at least for a while, more hours of processing to Amazon Web Services.