Freelancer marketplaces tend to be targeted at non-technical people hiring freelancers. Instead, I want to be able to see who has used specific tools I'll need and how they've used them.

Otechie indexes freelancers on Github based off of the contents of their public repos manifest files (currently only package.json). Besides other languages, I plan to add the ability to search for developers who have used services such as Circleci, Heroku, or Docker.

How are you retrieving this data? I wonder if it would be against the TOS of GitHub to clone public repositories in bulk and analyze them. I also believe that GDPR makes a service like this impossible in the EU without consent of the people on GitHub.