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.
Right, that's the point of the license. Essentially it stops other people from taking your code, packaging it as an app and selling it. Using it in your own business is fine though.
Only Retool alternative I have found so far that's not AGPL encumbered or open core.