Well, if you’re actually needing to compile the editor, you will need the source version, yeah. It won’t work as far as I know by just converting a binary only content project to source, and just trying to compile that.
Edit: You should be able to just get the Github version, compile it, and then open your project in it as normal - it should see it in the list of projects. It may need conversion as it might not consider it the same version as whatever your project was set up against.