GitHub, the code-sharing and hosting site based on the open source Git software version control platform, is getting a $100 million investment from the Andreessen Horowitz venture capital firm -- its first outside investment.

The money will be used to grow the platform to help users build better software together, an Andreessen Horowitz representative said. In making the investment -- the largest to date by the firm -- general partner Peter Levine in a blog post Monday cited faith in the company's founders Tom Preston-Werner, Chris Wanstrath PJ Hyett, and Git evangelist and GitHub employee Scott Chacon.

"They had a vision for a new way to develop software and created a new kind of company to pursue it. With only a handful of people in sales and marketing, the four grew the company to over 100 people, while growing revenue at nearly 300 percent annually -- and profitably nearly the entire way," Levine wrote.

Andreessen Horowitz's investment is significant, said IDC analyst Al Hilwa. "This is quite a unique arrangement. The sum is large and the particular alignment with Andreessen Horowitz is unique. The deal resembles more of a merger than a traditional venture investment," Hilwa said.

In addition to its code-hosting site, GitHub also has shipped applications such as GitHub for Windows and GitHub for Mac. Founded in 2008, GitHub offers public repositories for free but sells access to private repositories. GitHub CEO Preston-Werner wrote about the investment in a blog post and expressed ambitions to continue improving collaborative software development. "We want to keep changing the way software is developed for the better by making collaborating easier and sharing a no-brainer," Preston-Werner wrote.

GitHub's technologists took an old technology and "turned it on its head," according to Andreessen Horowitz's Levine. Rather than forcing development teams to deploy their own software change management (SCM) system, GitHub runs a single SCM in the cloud and eliminates management issues, he said. Also, GitHub organises projects around people rather than code. "By orienting around people rather than repositories, GitHub has become the de facto social network for programmers," he said.

Levine will join the GitHub board of directors. Andreessen Horowitz is perhaps best known for cofounder Marc Andreessen, who codesigned the Mosaic Web browser.