CWI designed many open source software programs. A few examples of popular software originating from CWI that can be downloaded for free are Python, MonetDB, Rascal and Matifus.

Python

Python is an open source programming language originally designed and developed by CWI in the 1990s, by Guido van Rossum. It is now used by tens of thousands of users in, for instance, web development (Google, Yahoo), games, graphics (Walt Disney Feature Animation), by banks, in science (NASA), software development, education and company software.
More information: http://www.python.org.

MonetDB

MonetDB is an open source column-oriented database management system developed by the Database Architecture group at CWI, one of the leading groups in Big Data research worldwide. It was designed to provide high performance on complex queries against large databases, e.g. combining tables with hundreds of columns and multi-million rows. Since 2011, column store technology as pioneered in MonetDB has found its way into the product offerings of all major commercial database vendors.
More information: http://www.monetdb.org.

Rascal

Rascal is a domain specific language for source code analysis and manipulation, also known as meta-programming. CWI researchers have started the design in 2010. It is currently being developed and tested at CWI. No formal release has been made yet, but alpha quality "previews" are provided on the Download page of http://www.rascal-mpl.org/.

Matifus

Matifus is a Matlab ® toolbox for 2D image fusion. It was designed by Gemma Piella, Henk Heijmans and Paul de Zeeuw (CWI) in 2004. Nitin Gupta and Anand Kumar (Indian Institute of Technology) wrote the graphical userinterface.
More information and download registration: http://homepages.cwi.nl/~pauldz/Bulk/Codes/MATIFUS/

CompLearn
CompLearn is a suite of simple-to-use utilities to apply compression techniques on discovering and learning patterns. This powerful approach can mine patterns in completely different domains. It can classify musical styles of pieces of music and identify unknown composers. It can identify the language of a text. It can discover the relationships between species of life and even the origin of new unknown viruses such as SARS. In fact, this method requires no background knowledge about any particular classification. CompLearn was originally developed at CWI by Rudi Cilibrasi, Steven de Rooij and others, based on the compression-based learning research of Cilibrasi, Paul Vitányi, and Ming Li. This method is used in many applications. More information: http://www.complearn.org/

CWI also contributed to other software and standards, including W3C web standards and fields such as XForms, (X)HTML, Semantic Web, CSS, SMIL and RDF.