Run-DMC were definitely not sellouts, they sang about Adidas because they genuinely loved them and grew up wearing them. They weren't paid until Adidas took the opportunity to promote them even further. They did reject Calvin Klein ("no friend of mine, don't want nobody's name on my behind")

Additionally, Run-DMC had tons of positive, supportive, pensive and wise lyrics about education ("I go to St. John's University / and since kindergarden I acquired the knowledge / and after 12th grade I went straight to college"), economics ("All day I have to work at my peak / because I need that dollar every day of the week"), hard work ("He gets better cause he knows he hasta / in 84 he'll be a little faster / cause only practice makes a real Jam Master"), and just being a good person ("here's another point in life you should not miss / do not be a fool who's prejudiced")

IMHO Run-DMC was easily the most inspirational and positive rap group of all time. And the best damn rappers period. RIP JMJ.

For the record, DMC were not sponsored or incentivized by adidas until well after the song was produced and distributed. Basically adidas jumped on an existing trend.