For example, it failed on this PR, but it doesn't look like there are any issues in it.

Seems the travis checking thing is choking on this dist due to it listing a .zip and not a git repo as source-url? Also, briefly looking through the source of the travis checker, I see along with assuming source URL is always a git repo, it's also assuming source-url field is the only one it's specified in.

Actually, source-url is an ecosystem extension and "proper" way to specify source is via "support": { "source": ... key, so the checker needs to check that too.