CEOs from Sleepycat, TrollTech, MySQL and JBoss.

Legally and technically you can also go from open source license to dual licensing. In open source projects where lot of contributors have copyright to their individual contribution, all these have to accept to enter into a dual licensing scheme.

LGPL is good for JBoss. Modification is contributed back to the JBoss core. Provides a stable base. But it is not viral. Software vendors would not accept the GPL because JBoss’ has a middleware product.

Quid pro quo philosophy at MySQL. GPL is best to serve that purpose. Nor perfect but the best available. GPL was added in 2000. MySQL is not middleware but a database, which makes a difference. On the GPL side mySQL saves money by having free help to produce the software. On the commercial license mySQL makes money by charging license fee.

Q public license invented by TrollTech in 2000. Shifted to GPL later because it protects and because it is widespread. LGPL is not suited for TrollTech.

Sleepycat public license. A proprietary license that is less than one page. Some licenses are better for dual licensing. The open source license should put obligations on the user that they are willing to pay to avoid. The commercial has to give warranties, updates, support and other things customers demand. An advantage of a dual-licensing scheme is that it is possible to provide clauses that makes the SCO threat irrelevant.

Sleepycat does not believe that a positive cost-benefit analysis will lead to that it is worth spending money on business that do not confirm with its commercial license. Serious businesses will pay to confirm with the licenses. Non compliant business probably wouldn’t have the money to pay for the license in the first place.