From https://github.com/MadRabbit/keyboard-genetics

"I used a series of articles from various online media. I don't have copyrights to provide them with this project, so you will have to use your own source."

and

"Create the text folder and fill it in with *.txt files which you'd like to use as the test data source. "

It would be interesting to see what a layout full of source code/terminal history would generate - although you'd have to take into consideration all variety of autocomplete functionality (tab key usage) in text editors to get accurate input data, not to mention window switching shortcuts etc.