Thanks for raising this question, @jdaviescoates.
I am personally not sure open-sourcing is critical here, as I think the first beneficiaries would be big cloud platforms (AWS, etc) that would then be able to host it and cut out any income for the developers. The current source available arrangement strikes me as probably necessary and appropriate.
I'm increasingly convinced that OSS as such is broken as a means of protecting against corporate exploitation, and it should not be celebrated as an end in itself. Based on my conversations with @girish, I think the single most important fact about Cloudron is that the company is bootstrapping (based on our subscription fees) and not seeking an exit. As long as that's the case, I think the community should support their self-defense through licensing.
Rather than fixating on licensing, it might be more relevant to all of us to discuss the possibility of an "exit to community" for Cloudron, in which ultimately the company we pay into becomes owned by—and accountable to—the people who rely on it. This could help ensure that the company we're paying into, and that is stewarding the code we depend on, doesn't get captured by forces beyond our control.