As the other poster mentioned, DBT is an open core product and I'm not sure how you'd use the cloud service on a local DB install anyway. Airflow and DBT don't really do the same things anyway.

DBT is open source and can be used entirely for free. They sell a hosted version.

Also DBT and Airflow are different tools, aimed at solving completely different problems. The Airflow competitor in this article is Dagster, which is also open source.

I'm not sure those two solve the same problem. Regardless airflow is an amazingly useful tool.

dbt-core is open source and can be used locally.