Licensing has taken various forms, ranging from the traditional proprietary license used by Microsoft, IBM, and Oracle; to Microsoft's somewhat less-restrictive Shared Source license to the all-access GNU General Public License (GPL), which has caused problems, Stein said.

"The GPL is sometimes considered viral in that it grows out to the entire software package," requiring the release of all code affected by it, he said.

Even licenses associated with Google, where Stein is employed, Yahoo and MSN are closed, he said. "Their software is also closed. It's proprietary; you can't get at it," said Klein.

In comparing Eclipse and Apache, Stein said Eclipse looked at the Apache model when being founded. Like Apache, which started with a Web server, Eclipse has expanded beyond its original mission, now being more than just an IDE. But Eclipse has paid staff while Apache is all-volunteer, said Stein.

"Our organizations [have] not been very close, but certainly, we're starting to see more cooperation between them" Stein said.