A FOSS solution to doing taxes.
This was a nice experiment to codify the tax forms (rather than use the XML definitions provided by the IRS[1]). It was intended to do a line by line translation of the English tax tax forms, performing calculations when lines were specified calculations. Form cross-referencing was also a feature, allowing for obtaining data from other forms/worksheets.
My personal interest in this has deminished due to Credit Karma's own tax system.