Code that is pasted from elsewhere

This license says contributors wrote the code, but there are plenty of cases where this doesn't hold. There are bits pasted from websites.

e.g.
https://github.com/ckan/ckan/pull/1251/files#diff-530e98d83857b6bd57795518ad4c2dbdR56

I think people are careful enough to ensure to add the reference and the licenses don't conflict, but can't be certain. I'm no lawyer, but it might be pertinent to admit this. A big company or government client may want assurances.
- Find copied code by grepping for attributions/licences and maybe using some sort of tool for unattributed bits.
- Ensure these are ok to include and relicense under AGPL
- Amend CLA to allow for this practise