[cyphar]

> Well a license is just a form of contract

Free software licenses (and some proprietary software licenses) are not contracts in any meaningful way. They do not require any of the tests of contract law (meeting of minds, bystander, willingness to be bound, etc) and are implicit agreements (to be fair, contracts can also be implicit but that's not what people are talking about when they say "contracts"). The reason you have to obey the GPL is because the only way you can do anything with the software is by obeying the terms of the license (assuming it's not dual-licensed). That doesn't smell or sound like a contract to me.

> Copyright assignment is more like a sales contract

Except free software copyright assignment gives you non-exclusive rights to licensing anyway (so you only lose the power to sue people, which is not something that software developers do regularly). In addition if you sign a contract to buy a car under the condition that you will drive it to Texas and you don't drive it to Texas, then the contract is voided. Same with houses, or anything else you could possibly sell.