On the dual-license model [LWN.net]

When people go looking for successful free software business models, the dual-license approach tends to turn up near the top of the list. With this model, a company releases a software component under a copyleft-style license so that all may make use of it. This company also offers the same software (or, perhaps, an enhanced version of it) under a paid, commercial license, allowing other companies to incorporate it into their products without the need to make their own code available. This model will clearly be most successful for software which works as a building block for larger systems. The dual-license model has been employed by companies like MySQL AB, Trolltech, FSMLabs, Sleepycat Software, and others.

The dual-license model can look like the best of both worlds. The free software community gets high-quality, supported code - and often good documentation as well. Developers get paid for working on that code. The company which makes all this happen gets to stay in business. That company's customers get (1) the use of the code in their proprietary projects, and (2) an immediate indication of what it is costing them to keep their own code non-free.

This model is not suitable for every project, and it is not without its disadvantages. One of the strongest of those, perhaps, is the disincentive it presents to potential contributors. A dual-license company can only accept contributions which it will be able to sell under its commercial license; in practice, that implies copyright assignments or some other form of explicit permission from each contributor. Some developers are happy to contribute code under such conditions - those contributions improve the free version of the package, and the developer still probably gets much more back than he or she ever could contribute. But others are less interested in contributing code which can be taken proprietary for somebody else's exclusive commercial benefit.

Another potential snag in the dual-license model was highlighted this week when Oracle announced its acquisition of Sleepycat Software. Like Innosoft (acquired by Oracle last year), Sleepycat provides a transactional engine for MySQL's database offerings. MySQL gets that code under a dual-license arrangement which, in turn, allows MySQL to include it in its own dual-license products. The result is that Oracle now controls two important components shipped by MySQL.

Sleepycat CEO Mike Olson says that neither the free software community nor Sleepycat's commercial customers should be concerned about this acquisition. But Mr. Olson spoke a little differently after the Innosoft acquisition:

Speaking at the Open Source Business Conference, SleepyCat CEO Michael Olson said he believes Oracle's takeover of Innobase, the Finnish developer of InnoDB, a discrete open source transactional database technology that ships with MySQL, is an acknowledgment of the growing importance of open source and of MySQL in particular. "Any attempt to disrupt a competitor is an acknowledgement that the competitor matters," Olson said. "And I think that acquisition was in significant part an attempt to disrupt MySQL's business."

(Thanks to Jim Thompson for the pointer to that article).

It is worth noting that neither acquisition can do immediate harm to the free software community. The code which was released under a free license remains free and cannot be taken back. The worst-case scenario would appear to be that developers could be taken off the projects, slowing or stopping the development of that code.

The situation might be a little more perilous for MySQL AB, however, and its customers as well. Oracle is now in a position to change the licensing terms for both database backends, or even to make them unavailable for dual-licensing altogether. And that points out an important aspect of the dual-licensing model: if you buy into the proprietary side of dual-licensed software, you are very much in the proprietary software world. And, at that point, you can be impacted by policy changes by your supplier - or by their suppliers as well.

Buying proprietary access to dual-licensed software may still be the best path for many companies. It can enable the use of high-quality, community-reviewed software at a reasonable price. But dual-licensed software should not be seen as free software with some commercially inconvenient strings removed. It is proprietary software, with all the risks that come with the proprietary model.

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