Each original source document (code and documentation, but excluding the LICENSE and NOTICE files) SHOULD include a short license header at the top.
Here's what that license header should look like:
Copyright 2018 OmiseGO
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
Things to consider:
Some files have been contributed by users that have not signed any form of CLA. Should we have new and existing contributes sign a CLA?
The pre-Apache 2.0 licensed code is probably All Rights Reserved, although I'm not sure if this applies to code contributed by other people.
According to Applying the Apache License, Version 2.0:
Here's what that license header should look like:
Things to consider: