Adobe Lightroom The Diagonal Method was built in beta version of Lightroom 1.1. in February 2007 and released for the public in June 2007. Adobe did not ask for permission before or after.
Adobe Photoshop CS The Diagonal Method was built in Photoshop CS6 in the year 2013. Adobe did not ask for permission before or after
Gimp From version 2.8 the Diagonal Method is a standard tool in Gimp. It is called "Diagonal lines".
Paint Shop Pro, Picture Window en Inkscape Since 2009 there are also DM scripts for PaintShop Pro, GIMP and Picture Window Pro, and since 2010 also for Inkscape.