GlitchTip isnt a fork. Its a reimplementation of Sentry by folks who I had never had interactions with (afaik) before we migrated to BUSL. They leverage our SDKs, and maybe they've vendored in some of our original code (hopefully correctly applying the license), but you can browse the source and clearly see its not Sentry. It turns out its quite complicated to fork, build, and maintain a project at the size of Sentry when you arent familiar with it, and didnt help build it.
Theres a lot of nuance in Open Source, and I will probably write more about this part of Sentry's history, but unlike say Terraform, Sentry (the service) was almost exclusively developed by myself and other employees of the company.
Early versions of it I beleive used more Sentry code. If I recall correctly their initial release was basically a renaming of the open source sentry code. It has taken its own direction since.
Theres a lot of nuance in Open Source, and I will probably write more about this part of Sentry's history, but unlike say Terraform, Sentry (the service) was almost exclusively developed by myself and other employees of the company.