Does inbound=outbound apply to GPL-family without a CLA?

Question

The traditional expectation for contributions to a free software project are "inbound=outbound" [1] [2]. That is, if the project is under license X, contributions are made under license X.

Does this apply to a project released under any/all of the following licenses with no additional CLA?

• LGPL v2-only
• GPL v2-only
• LGPL v2-or-later
• GPL v2-or-later
• LGPL v3-only
• GPL v3-only
• AGPL v3-only
• LGPL v3-or-later
• GPL v3-or-later
• AGPL v3-or-later

I am not concerned with compatibility beyond that, just that in each case that contributions are "by default" the same GPL-variant as the original project.

Answer 1

Yes, submissions to a GPL codebase remain under the same GPL variant. This is specifically because of the copyleft mechanism. For example, from section 10 of the GPLv3 license text:

Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License.

This applies to all listed variants of the GPL (version 2/3, only/or-later clause, A/L/GPL variant). Specific modifications to the license terms are sometimes allowed (for example, by the "or later" clause), but "by default" the terms remain the same.