I'm happy to hear the Microsoft.SqlServer.TransactSql.ScriptDom is now an open-source project. I submitted Microsoft feedback to make it open-source a few years ago and it's nice to see it was finally implemented. The GitHub project will also facilitate reporting ScriptDOM issues and suggesting enhancements for users that don't want to go so far as to make code changes themselves.
The associated NuGet package is especially convenient for situations when only the Microsoft.SqlServer.TransactSql.ScriptDom.dll is needed for code analysis (I use it with PowerShell in a CI/CD pipeline). Previously one had to reference the Microsoft SQL Server Data-Tier Application Framework package, Microsoft.SqlServer.DacFx, which includes the ScriptDOM assembly as part of that larger component.