Saxon has been under development since 1998. Until release 9.3, most of the code was written by one person, Michael Kay, which has resulted in a high level of design integrity. More recently O'Neil Delpratt has joined Saxonica's development team and has contributed extensively to the development of Saxon 9.4 and 9.5.
Saxon was originally written to support an internal project in ICL (now part of Fujitsu), and ICL continued to sponsor development of Saxon until Michael Kay left the company in January 2001. ICL chose not to market it as a commercial product, but to make the code available to the public under the Mozilla public license. From 2001 through 2003 Michael Kay worked for Software AG, who continued to sponsor the development of Saxon as an open source product.
In March 2004 Michael Kay founded Saxonica Limited to provide ongoing development and support of Saxon as a commercial venture. Saxonica continues to develop the basic (non-schema-aware) version of Saxon as an open source product, while at the same time delivering professional services and additional software (Saxon-PE and Saxon-EE) as commercial offerings. The commercial product incorporates the code of the open-source product in its entirety, with the addition of schema-processing technology, and is produced in accordance with the provisions defined by the Mozilla Public License.
The port of Saxon to the .NET platform was pioneered by Pieter Siegers Kort and M. David Peterson, without any involvement from Saxonica. Their work was absorbed into the Saxonica product line from Saxon 8.7 onwards. The Saxonica product used the same approach as the previous Saxon.NET product for cross-compiling the code into CIL assemblies. In addition, however, it provided a new .NET API for use by C# and other .NET applications, and made much greater use of .NET services such as collations and regular expression processing. This integration was done by Saxonica with generous advice from M. David Peterson. The project would not have been possible without the IKVMC cross-compilation technology developed by Jeroen Frijters, as well as the GNU Classpath developed by a large team of individual enthusiasts. The use of GNU Classpath was subsequently discontinued and replaced with OpenJDK.
It is unfortunately not possible to release Saxon-HE under any license other than the Mozilla Public License. Although the amount of code from external contributors is small, it is not practically feasible to obtain the necessary permission from all these people to release under a different license. With Saxon 9.5, Saxonica has moved forward to the Mozilla Public License 2.0; the differences are only of interest to lawyers, but the language is more concise and readable.
In 2010 Michael Kay started work on a prototype of Saxon-CE, a cut-down version of Saxon cross-compiled to run in the browser using the Google Web Toolkit (GWT). This now provides the first implementation of XSLT 2.0 to run client-side. Phil Fearon worked with Saxonica for a year to turn the prototype into a product, which was finally released in June 2012. Early in 2013 Saxonica decided to make this product open source.
The name Saxon was chosen because originally it was a layer on top of SAX. Also, it originally used the Ælfred parser (among others); Ælfred of course was a Saxon king.