This indeed is mostly a wrapper around guac. But we did design a custom client protocol for speed.
https://www.apache.org/foundation/license-faq.html#WhatDoesI...
> You must give any other recipients of the Work or Derivative Works a copy of this License
They're pretty clear on attribution being in the source only in 4c:
> You must retain, in the Source form of any Derivative Works that You distribute, all copyright, patent, trademark, and attribution notices from the Source form of the Work, excluding those notices that do not pertain to any part of the Derivative Works