Finalize License Header Management

[danehans]

Kubernetes and many other projects include a license header in each project code file while Envoy only requires license headers at the project root. With #84, EG will follow the Kubernetes approach. Determine if this approach is needed, and if not, follow Envoy's approach to license header management.

cc: @lizan @mattklein123

[mattklein123]

It is not needed and just creates extra clutter and overhead. I would follow the envoy approach personally.

[youngnick]

Reopening this one because we've had something come up.

In building out Envoy Gateway, we're lifting reasonably large chunks of code from other projects (mainly Contour at the moment, but probably others as well soon), so we need to ensure we're abiding by the Apache license from those projects, which requires code attribution.

Because the attribution will only be in some files, it makes sense for us to have a per-file copyright callout at least, even if it doesn't have the full "get the Apache license here" callout. (Personally, I think text storage is relatively cheap and we should err on the side of just including it, but it's not a strong preference).

Reopening here so we can discuss and figure out a format for a per-file license header, keeping this in mind.

[skriss]

I'm not an expert here, but perhaps something like the following is sufficient? Would be much easier than having to do things file-by-file.

https://infra.apache.org/licensing-howto.html#example-notice
https://github.com/apache/httpd/blob/trunk/NOTICE

[skriss]

Also reading https://github.com/cncf/foundation/blob/main/license-notices.md which was linked from #134, which has some guidance (unfortunately it's more file-by-file).

[youngnick]

Yes, rereading that license-notices file, it seems clear that we have to bring in any copyright notices from files where we've imported significant code (Contour being the main example for now), and also include "the function was sourced from x" as well.

Because of this, I think that the simpler licensing method that Envoy Proxy uses won't work for this repo. There's too much license complexity to capture, we need to ensure that every file has a copyright and license notice.

It's an up-front effort cost, with an additional one for each new file. We're going to need a slightly more clever license check too, I think.