I agree sourceMaps shouldn't be exposed and they also bloat up production code. The reason we have them exposed for the time being is for debugging purposes in open beta and we intend to remove it out of production in our upcoming weekly release.

As long as there is no license attached, you are essentially not allowed to use it anyway.

Shipping source maps allows for better error-reporting instrumentation, and can also be a great help if you need to debug an issue you're not able to reproduce in a local or staging environment.