LAS VEGAS -- Silverlight 4, Microsoft's software for Web multimedia, is now on 60 percent of all Internet-connected devices, the company said. A year ago, the software was at 45 percent penetration.

Scott Guthrie, corporate vice president for the .NET Developer Platform at Microsoft, said the software has reached the release-candidate milestone, and the final version will come out in April. The software will be made open source, he said.

Silverlight competes with Adobe's Flash software, which is popular for presenting video and animation on the Internet. NBC used Silverlight during the Winter Olympics to stream events on the Web.

EBay is opening the equivalent of an iTunes app store for developers to sell Silverlight software.

Guthrie made the announcement in his keynote speech Monday at MIX, the Microsoft conference for Web developers. The conference will continue through Wednesday in Las Vegas at the Mandalay Bay convention center.