The traditional expectation for contributions to a free software project are "inbound=outbound"  . That is, if the project is under license X, contributions are made under license X.
However, I'd like to make a simple statement about this in my README, just for clarity. I don't want to say "inbound=outbound" because that phrase is opaque without a lot of prior knowledge. Is there a well-established / recognised phrase for stating this?
(I'm looking for a standardised phrase for a human reader, not a legal solution which might be license dependant   .)