This situation is pretty different from Qt. Qt is a software library, where a GPL license essentially requires the library user to release their software under a GPL-compatible license.

It is also unclear how well this works for the Qt Company, based on the changes that were implemented a while ago (e.g. they are no longer releasing LTS versions as open-source.)

The Foxglove app is mainly used by end users, who in most cases are not redistributing it (or have no problem redistributing it under GPL / AGPL), so this license change would not solve the original problem: the financing of future development.

Financing the development of open-source software is a hard problem as evidenced by this announcement.

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