There isn't a license because the schema bundle is all considered "documents" that are covered by copyright. The DMTF copyright policy is shown at www.dmtf.org/about/policies/copyright - and the relevant portion I've copied here:
DMTF is a not-for-profit association of industry members dedicated to promoting enterprise and systems management and interoperability. Members and non-members may reproduce DMTF specifications and documents for uses consistent with this purpose, provided that correct attribution is given. As DMTF specifications may be revised from time to time, the particular version and release date should always be noted.
You should consult with your legal representative concerning any use.
This question has come up before regarding the Message Registries (same answer). We'll take a look to see if something similar could be done for the schema files.
Thanks Jeff. Does the copyright allow for distribution? If we were to distribute a Redfish implementation including these schemas to a vendor contracted to do development & testing on the Redfish implementation?