Sun Microsystems has hit back at criticism of how it chose to open up the source code for the Solaris operating system.

"I don't understand what the beef is here," chief executive Scott McNealy said during an event at the company's headquarters. "It's a tempest in a teapot."

Sun last week released the source code of its Solaris operating system under the new Common Development and Distribution Licence (CDDL). The company also promised to indemnify developers and users who submit themselves to the licence.

The catch is that Sun will not make any promises to those who use the Solaris code and choose not to adhere to the CDDL.

It will also not guarantee to refrain from using its patents against developers working on open source projects in general.

This has caused representatives from the Free Software Foundation to speak out against the Sun licence. The Foundation is joined by open source advocate Bruce Perens.

On a forum on Slashdot, Perens called Sun a "spoiler" that is trying to fragment the open source movement by creating a licence that deviates from the General Public Licence (GPL).

Sun chief operating officer Jonathan Schwartz denounced the comments. "It's those that believe that everything must be GPL. The open source community is far larger than just the GPL community," he said.

"We think that we have done more than any other company in the industry in protecting the code that is out there with our intellectual property protection, as well as volunteering more source code than any other company."

In contradicting news reports stating that Sun would take a more gentle approach to open source developers, McNealy also categorically denied that Sun will make any promises not to use its patent portfolio of non-CDDL open source projects.

"Sun has an obligation to its shareholders to leverage and protect its intellectual property," he said. "We are granting [access to our intellectual property] to people who are responsible and who are signed up licensees of the CDDL."