I wouldn't cahnge the permissions of that directory as it is a system directory. Create a directory under src:
mkdir -p /usr/local/src/courier
Move the tarball:
mv /usr/local/courier-imap-3.0.3.tar.bz2
Change the permissions:
chown -R comp:comp /usr/local/src/courier
For more information on permissions:
http://wiki.linuxquestions.org/wiki/Permissions