You can't deployed the apps generated in any useful business capacity so it is not truly free except for a minority of personal users (or if you are in a country where IP rights are not easily enforced).

These platforms' primary customers and audience are enterprises and companies. The open source part is a red herring. It is not "free" to use in any sense for most organizations unless you are a non-profit with a majority of network infrastructure being under copyleft software. Don't be disingenuous, there is a very big difference for a web application builder and PaaS under rigorous viral copyleft vs e.g. a generic web server that will never be seen or utilized directly by users.

AGPL makes something free as in "non-encumberable", it doesn't leave you free to do more or less whatever you want with it like the MIT or BSD licenses.