Sun Microsystems has opened the door to adopting the General Public Licence (GPL) for its Solaris operating system. 

Chief executive Jonathan Schwartz raised the idea at a company event marking the release of Java SE and Java ME components under the GPL.

Rich Green, Sun's executive vice president for software, said in response to a question from Schwarz: "Today's event and the feedback that we received casts a very positive light on our choices going forward.

"The familiarity and comfort level with the licence we've chosen for Java is going to drive a lot of the decision making for the existing technologies that we've open sourced."

Solaris was released early last year under Sun's open source Common Development and Distribution Licence (CDDL), prompting a storm of criticism. 

The CDDL offers a patent grant to all developers and users of CDDL software, but does not extend protection to projects outside the CDDL.

Contrary to the GPL, Sun's open source licence also lacks a provision that requires developers to publish the source code of any adjustments made to the software.

The limited patent protection drew fire from open source advocate Bruce Perens, who referred to Sun as a "spoiler" out to fragment the open source community.

Sun hit back at the CDDL critics, claiming that the GPL is unfair and predatory because it requires developers to publish changes to the source code. 

Schwartz, who was chief operating officer at the time, claimed that the GPL was used unfairly to force developers to share their work because the creators had a hidden agenda of forcing a social model on the world.

Sun now seems to have changed its views on the value of the GPL. When the vendor released its Glassfish application server last year, it did so under the CDDL.

Today it added the GPL as a second licence to the Glassfish code, allowing developers to choose either. A similar scenario could be a likely future for Solaris.