I nearly decided to hack in a Public Mode myself last year, I'm glad it's finally implemented!
This has prompted me into getting back to work on my KanBan SPA, that hooks into GitLabs issues api. I do wish they gave the api a bit more love in this release, but I can't really complain: My $20/m VPS gives me self-hosted Github, Dropbox, and Gmail/Gcal/Contacts "clones". Not bad!