// contain duplicate certificates, or that use PEM block headers.
  //
  // Users of ClusterTrustBundles, including Kubelet, are free to reorder and
  // deduplicate certificate blocks in this file according to their own logic,
  // as well as to drop PEM block headers and inter-block data.
  optional string trustBundle = 2;

are still covered by their original MIT license, with the additional
copyright staring in 2011 when the project was ported over:

    apic.go emitterc.go parserc.go readerc.go scannerc.go
    writerc.go yamlh.go yamlprivateh.go

Copyright (c) 2006-2010 Kirill Simonov
Copyright (c) 2006-2011 Kirill Simonov

Permission is hereby granted, free of charge, to any person obtaining a copy of