Determine a collaborator's permissions (to an organization repos) via the api?
If you want to check whether you have push access to a GitHub repo, you can use the repo endpoint:
GET /repos/:owner/:repo
If your request includes your authorization information (either including your account credentials or an OAuth access token), the permissions field will give you the information you're looking for:
{
'admin': False,
'push': False,
'pull': True
}