The new Lotto website is now online, and it is open source. It is built on the Silverstripe CMS and web application platform. The site involves a fair amount of money changing hands, and is an example of a transactional website performing a government run and managed activity: i.e. it is a crown entity operating under an Act.
The previous site was based on the proprietary (but now dying) Adobe Flash technology. The new site is web standard HTML, generated by the SilverStripe CMS. Unfortunately, the underlying Lotto gaming engine is unchanged and sadly it is probably not open source (yet), but the trend towards open source is clear!
More information is available on the Silverstripe website.