gh_org_repos.py

from github import Github
import json

org = 'place-org-name-here'
gh_token = 'place-gh-token-here'

g = Github(gh_token)
repo_list = g.get_organization(org).get_repos()
data = map(lambda repo: { 'repository': repo.name, 'last_update': str(repo.pushed_at) }, repo_list)
with open('output.json', 'w') as outfile:
    json.dump(data, outfile)