When comparing:

[ ] implement a restful API for http://service/post/postid
a PUT should insert/update a post
a POST should insert the post
a GET should get the post

and https://github.com/abramhindle/CMPUT404-project-socialdistribution/blob/master/example-article.json#L13, there are no functional differences.

These endpoints are redundant and are most likely a result of @berjansk not realizing that a pre-existing call was defined in project.org for the same purpose, or a typo. My proposal would be to update the project.org specification of http://services/post to use http://service/posts as well since using the plural of post is the normal REST convention anyway and it'll bring it back in line with example-article.json.

author/ should be authors/ as per idiomatic REST.

As an author, posts I create be public