Since they were developed by several people with different skills and interests, both code bases use a combination of free software/open source programs.
The data processing pipeline looks like this:
Data from http://www.parliament.uk (and now http://www.parl.gc.ca)/
is parsed by a Python script, which outputs XML.
The XML is loaded by a Perl script into a MYSQL database
PHP scripts present the information to end users and provide interactive functions
Because the MP and proceedings data is stored in XML between stages, it is available in a format suitable for use by other projects. The UK group already provides this data to research organizations.