Can't find MIT/GNU Scheme in Applications after install
You can confirm where it was installed in /Applications by using Terminal.app:

cd /Applications
ls -lt | grep -i cheme


This should print the name of the directory where it was installed (which should be MIT:GNU Scheme). You can access it from the command-line by adding the following directory to your PATH: /Applications/MIT\:GNU\ Scheme.app/Contents/Resources.