View the original community article here
Last tested: Aug 28, 2020
Not if you want it to work consistently! Users who are signed into Github and have access to the private repo will be able to see the custom vis, but if they are not signed in to Github, the custom visualization will not work, and Looker will not tell them why. Furthermore, PDF and PNG downloads of the custom visualization will also fail, since Looker will not sign into your Github account to generate the file. More detail:
At the time a browser is loading a Looker dashboard page, it will make network requests to fetch the custom visualization javascript source. You will need to host those files somewhere that can be reached by any browser that can load your dashboard, including the “Headless” browser that Looker uses internally to generate PDFs and PNGs. Since there’s no way to guarantee that everyone who visits your dashboard is already signed-in to github with access to the private repo, you will probably need to “publish” the custom visualization source code somewhere else.
This content is subject to limited support.