Hmm, other packages that are installers for non free software (e.g. flashplugin-nonfree , ) also seem to live in contrib. IMO they are if anything worse because they download and install non-free software without further user interaction.Then this is worse, this package should live in non-free.
My reading of the policy is that as long as the contents of the package itself is free the package can be in contrib but the policy could certainly do with clarifying.
ccing debian-policy for wider input