https://github.com/gcp/leela-zero
Of course, it isn't as strong as AlphaGo Zero because it doesn't have Google's training resources, but they have plans:
One reason for publishing this program is that we are setting up a public, distributed effort to repeat the work. Working together, and especially when starting on a smaller scale, it will take less than 1700 years to get a good network (which you can feed into this program, suddenly making it strong). Further details about this will be announced soon.