Yahoo announced this week it has opened its doors to innovation in general, and developers who want to build applications in particular. For the first time ever, and six months after joining Google’s OpenSocial program, Yahoo made an official invitation: “We’re open. Have it.”

In spring this year, Yahoo agreed to join Google’s OpenSocial platform, which aims at building an infrastructure for the social web. This enables developers to create applications for social-networking sites.

MySpace welcomed Yahoo! as an important addition to the OpenSocial network, stating that this alliance will provide developers with the necessary tools to make the Internet faster and “foster more innovation and creativity.”

At the time, Yahoo said it expected OpenSocial to become a tool that fuels innovation and makes the web more relevant and more enjoyable for millions of users. The decision to join the open platform was driven by the willingness to open up their network to innovation, embrace and enhance the social relationships between users, and ultimately offers users “the best of the web.”

Developers are invited to join the initiative and start using the data Yahoo has put at their disposal to create web sites or new applications into Yahoo.

“Reaching this step in our Yahoo Open Strategy has been a significant effort, requiring hundreds of developers in offices around the world,” Jay Rossiter wrote in the blog announcement. “We’ve even worked hand-in-hand with Google, MySpace, and many other of our traditional competitors as partners in this effort. We mean it when we say we’re open!”

With the help of OpenSocial, developers will be able to create applications to access social networks and update feeds, and with the help of a common API, they will also be able to make them available to users.