Oracle mention this on their website:

  This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means.

DevDocs is just a hobby of mine and I don't want to waste my time on a documentation that I may have to remove. If Oracle is willing to grant DevDocs a license (I haven't asked them) I'd gladly add the JDK docs to it.