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Open source databases and commercial software

The growing prevalence of open source database systems has made them increasingly interesting for commercial deployment.
The various license models however do not principally mean that the deployment of an open source database system is always free of charge.

This article analyses the license models of the most popular open source database systems and the effects on the deployment with commercial software, which is not open source, according to the GPL (General Public License).

Following candidates have been selected for analysis:

  • Firebird: Relational database for the new millennium
  • PostgreSQL®: The world´s most advanced open source database
  • MySQL®: The world´s most popular open source database


The following expositions are not the author´s personal valuations, but taken from the websites of the respective project home pages.

1. FirebirdSQL

The Firebird project home page quickly clears up the question of deployment costs:

"Firebird is completely free of any registration, licensing or deployment fees. It may be deployed freely for use with any third-party software, whether commercial or not."

So, it is possible to distribute the Firebird server unconditionally free of charge with any sort of software. Details can be found in the IPDL and the IPL license. These are however based on the Mozilla Public License Version 1.1.

2. PostgreSQL®

Due to the equally clear general conditions, the free deployment of the PostgreSQL® server was then reviewed. The following general conditions can be found on their website under About – Licence:

"Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies."

On this basis every PostgreSQL® user may distribute this server in any combination with his own software to customers or any other parties. There is an interesting reference on their website4, why the PostgreSQL project chose the BSD license and explicitly not the GPL license. There have been various discussions regarding this in their forum.

3. MySQL®

The MySQL® license model is considerably more complex, as there is not just a single license for the MySQL® server, but various versions, depending upon the area of application.

This analysis is based on the current information and examples found on the supplier´s, MySQL AB, internet server. The exact wording can be taken from the license conditions of the respective deployed versions, especially as the license conditions for the MySQL® server have changed over the years.

For open source applications developed and distributed according to the GPL license, the user may deploy MySQL® according to the conditions of the GPL license. If you are developing and distributing open source applications under an OSI-approved License, but not the GPL, MySQL® provides the GPL License with a FLOSS Exception. Examples for OSI-approved license models include LGPL, BSD license and others. A list of licenses permitted by the producer, MySQL®, can be found on their website.

Deployment of the free MySQL® GPL version is only permitted for software producers, when the software is published under one of the license models mentioned. Any other use is only allowed with a commercial license.

Further case studies can be found on the website; however these also do not fully answer all questions. They offer the following examples where a commercial license is requisite, as these are considered to be distribution:

  • Selling software that includes MySQL® to customers who install the software on their own machines.
  • Selling softwarethat requires customers to install MySQL® themselves on their own machines.

Irrespective of whether the MySQL® server is delivered with a third-party application or not, if the commercial software requires MySQL® to be installed, a commercial license is required.

  • Building a hardware system that includes MySQL® and selling that hardware system to customers for installation at their own locations. The author does not wish to assess here the effects of this regulation on a PC with preloaded Linux® distribution and MySQL®. The licenser´s statement is however perfectly clear.
  • If you include the MySQL® server with an application that is not licensed under the GPL or GPL-compatible license, you need a commercial license for the MySQL® server.

Conclusion

MySQL®´s arguments are generally based on the predication that by using the commercial license, it is possible to avoid having to also publish third-party software as Open Source. This statement certainly applies by all intents to the deployment of MySQL®, in consideration of MySQL®´s dual licensing conditions.

This argument however does not apply to the deployment of the Firebird and PostgreSQL® servers. These allow both the free use as well as free integration into installation routines in third-party commercial software without any limitations.

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