Students with computer science experience get a more advanced course that is explicitly designed not to make them more competitive in second-year courses (instead, it starts on material that will re-appear in third-year courses). Students with no computer science experience get their own intro course. And there is yet another "green" intro course tailored to biological applications.
The article suggests that these practices help level the playing field in the first two years of the computer science major, by which point people have enough invested to finish.
On reflection, these aren't new suggestions. Unlocking the Clubhouse, a 2002 book on women's experiences studying computer science, made similar recommendations. But I guess most colleges are struggling to handle the glut of first-year computer science students, let alone teach more courses to encourage more of them.