Sun is close to delivering on its open source promises, so let's get the good news out of the way first. Five million lines of code -- the heart of one of the most mature and highly specified operating systems around -- are to be released into the open. More than 1600 patents are to be declared available to all, almost without reservation. With OpenSolaris, Sun is releasing a huge body of work for everyone to look at and learn from -- and that alone is a historical move deserving applause.
When deciding how useful this will be, some scepticism is still required. As with many of Sun's recent moves, it is not clear whether the company's internal motivations match its public statements. In particular, the Community Development and Distribution License under which the software is published is not compatible with the GPL -- you can't mix code between the two licences -- nor do GPL developers get the unfettered patent use that is granted to CDDL developers. Also, Sun demands co-ownership of copyright of anything contributed to OpenSolaris itself. Such considerations set significant limits to the utility of the release.
The CDDL is otherwise impeccably liberal, placing few restraints on open or proprietary use of code so licensed. Sun wants a development community to grow up around OpenSolaris. Community is all, whether it is the regimented armies of Windows developers or the warrior-priests of Linux. Without the continuous intellectual input of many thousands more minds than any one company can directly marshal, even the best platform can fossilise in no time. But the CDDL effectively excludes the majority of open source development: existing GPL developers will have to start from scratch if they want to play. They'll have to choose their tribe.
The GPL isn't all of open source, but it has been peculiarly effective. Other communities drive successful products, such as the continually underappreciated BSD, but the way in which the GPL safeguards creator rights while encouraging true openness fits developmental psychology just as well as it promotes technical excellence. Sun has yet to show whether CDDL can provide as conducive an environment as the GPL for those who believe open source is the best way forward for software.
In the long term, these concerns will fade. The genie is out of the firewall, and over time the ideas and techniques in OpenSolaris will prosper or fade according to their Darwinian fitness within the open world. We will all benefit from Sun's revelations. By locking out the greater part of the open source community though, Sun will not get the rewards it so clearly feels it deserves, rewards it so nearly does.