You provide some code. The other entity (the project) provides attribution and other things depending on the specific license.
Promissory Estoppel only comes in to play if one side doesn't provide anything of value, and so the bar of consideration isn't met. But to my knowledge, licenses already meet the bar of consideration, so promissory estoppel doesn't matter.
Money isn't the only thing of value. The exchange of one good or service for another good or service is still consideration, no matter what. And "attribution" and "the promise to hold harmless" are of value.
The license does have consideration.
You provide some code. The other entity (the project) provides attribution and other things depending on the specific license.
Promissory Estoppel only comes in to play if one side doesn't provide anything of value, and so the bar of consideration isn't met. But to my knowledge, licenses already meet the bar of consideration, so promissory estoppel doesn't matter.
Money isn't the only thing of value. The exchange of one good or service for another good or service is still consideration, no matter what. And "attribution" and "the promise to hold harmless" are of value.