I believe you’re using technology to mean a concept (such as the git version control system). Which is valid, but I’m using the other meaning, an implementation or solution of the concept, which can certainly differ.

The two solutions have similar functionalities (git remote storage, action runners, issue tracking,etc), but for this use case (a hosting service) it is important that forgejo is copyleft while gitlab uses the MIT (an as-is) license.

If they used gitlab they could not stop gitlab from antagonistic development and this business could not provide as much trust to their users of continued improvements from the underlying git technology they are hosting.