Just in case... which version are you trying to install?
You mention "MzScheme," but don't let the arclanguage.org front page fool you. Arc works on up-to-date versions of Racket, not just the old MzScheme 372. See https://sites.google.com/site/arclanguagewiki/ for more comprehensive installation information.
I see some useful-looking Web search results for [Racket on Raspberry Pi], and they're much more recent than 2007.
