5 years from now when GitLab is acquired by Google we'll have to migrate again.
In other words, I don't know how much use it is to fork Gitlab if the community around it is dispersed. Git is already based around decentralization, and I don't see how running my own instance of Gitlab makes it any less disruptive when the most popular instance of Gitlab is disbanded.
Edit your CI scripts. Your CI should not be dependent on Github to work, besides maybe pulling code from it. But then it's just a simple change.
I edit my CI scripts almost daily, until the workflow is acceptable. I try all the others constantly, but it's a headache and needs weeks of time until it works good enough. Github only hosts the results and releases, but still.
Just last week I spent again a full day to get the encrypted auth working for github deployment from some random new CI. My CI's do work together with connected hooks, e.g. if appveyor and travis passes, merge to master, then appveyor deploys the binaries to github, then the release is published, which sets a tag, which triggers travis to make distcheck and deploy to the very same release on github.
On github I have static pages with custom domain names for free. On github I can host releases and dailies for free. Someone needs to pay for it. Better a big company which backs this.
I'm a bit sceptical with Microsoft as I'm sceptical with Google. You can never trust PM's in big companies. But so far I give them the benefit of doubt, they clearly love github (unlike google which didn't love code.google), and we'll all see.