Sun Microsystems has officially released the source code for its Solaris 10 operating system by launching the opensolaris.org website. 

The move allows developers to customise the operating system for specific environments, and sell it without having to pay licence fees to Sun.

Now that the code is available, Sun said that it will measure the success of the release by the size of the developer community it can gather around the project.

Collaboration with that community will be a major challenge, acknowledged Sun chief operating officer Jonathan Schwartz.

"You cannot think up things in the ivory tower and descend upon the masses; delivering a lump of code is not going to help much," he explained.

The company has always positioned Solaris 10 as direct competitor to Linux. In a conference call about the open sourcing of the code, Schwartz once again took a jab at Linux.

He described the General Public Licence (GPL) as " punitive" and claimed that Open Solaris "allowed individuals to build products free from any obligations".

Although Solaris and Linux are both open source operating systems, different licences govern the two software packages.

Linux uses the GPL while Sun has created a new Common Development and Distribution Licence (CDDL) for Solaris, which is sometimes referred to as a 'commercial open source licence'.

The main difference between the two is how they treat adjustments to the code made by individual developers or companies. The GPL requires developers to share their code with the world, while the CDDL lets developers keep the source code of their work secret.

The latter is a major benefit for enterprises wanting to incorporate open source code into products without giving away trade secrets.

Occasionally developers, by intention or accident, violate the code sharing provisions of the GPL. Last April a German court granted a preliminary injunction against security firm Fortinet for violating the GPL by hiding Linux in its source code without making the code available.

Meanwhile some parties in the open source community have been highly critical of some of the CDDL's other terms. 

The licence provides a protective umbrella to safeguard developers from patent claims by third parties. But the provision is available only to developers that work on Solaris under the CDDL, and not to parties creating a proprietary version of the software.