YScript is a language for the representation of statutory text for generating expert systems. It is a new version of a previous tool called ysh (Why Shell). YScript is the scripting language used by DataLex.
A user manual is available at AustLII.
According to this paper, YScript is available under the Affero open source license. Source code can only currently be obtained directly from the author, Andrew Mobrey, but I am advised that a public repository is forthcoming.
See also YLegis.