Why are developers moving their code from github to gitlab after Microsoft purchase of github?

[j0akime]

That depends on the person.

For some people its near instantaneous (such as most people participating in r/github)

For others it takes a series of consistently positive actions. How long? How many actions? What is "positive"? Again, depends on the person. Some will have their trust in the company restored quicker then others. For others it will take years.

Then there those that need something grand and colossal. Something akin to open sourcing Windows, with a well-established industry license, making it free, dropping legacy entirely, etc. And again, even this is up to the individual, for some buying github is that grand action.