ATLAS Rev. 6 AR15 A1 Upper Receiver for Rimfire (https://www.thingiverse.com/thing:2948289) by DangerCat5 is licensed under the Creative Commons - Attribution license.
http://creativecommons.org/licenses/by/3.0/

Daichi .22 LR Upper Reciever for the AR-15 by nguyenkvvn inherits the Creative Commons - Attribution license.
http://creativecommons.org/licenses/by/3.0/