In this case, there is nothing at all wrong with a GPL license. Everyone is answering from the perspective of a software company. That isn't who this product seems to be targeting. It's targeting businesses that sell physical goods and need a virtual storefront to do that. They aren't looking to fork this and repackage it as a different product. The purpose of it being open source at all is so they can more easily self-host it. If you self-host an application you don't fork and modify, there is nothing for you to publish. The source was already published by the person you got the code from in the first place.
For an app like this, that would typically be configuration in the database. (Think WordPress; are you writing your marketing copy in plugin source code or are you writing it using the page editing functionality?) The AGPL doesn’t require you to publish your database.
