Colab can load public github notebooks directly, with no required authorization step.

For example, consider the notebook at this address: https://github.com/googlecolab/colabtools/blob/master/notebooks/colab-github-demo.ipynb.

The direct colab link to this notebook is: https://colab.research.google.com/github/googlecolab/colabtools/blob/master/notebooks/colab-github-demo.ipynb.

To generate such links in one click, you can use the Open in Colab Chrome extension.