As I understand it you're only bound by the open source terms included with the software at the time you started using it - - basically if you modify the code you're bound to release your changes if you redistribute the software. They cannot change the version you're already using retroactively.
Was the license ever valid though, if the copyright owner didn't issue it? If I stole a car, then signed a contract giving you the car for $1, then would you be able to keep the car?
No, you'd have to give them the car, because the rightful owners are denied a car by you keeping it. But be careful, licensing doesn't fall under traditional ownership/theft rules.
If the deal appears to be too good then you can be charged with handling stolen goods, which is a loophole closer for people palming off stolen items to friends for almost nothing. If you pay what is considered a going rate for an item that turns out to be stolen you are most likely not breaking the law, though of course that doesn't mean the property is yours or that you would be compensated for it's removal from your ownership. Note this is relevant to UK law, no idea about other jurisdictions.
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As I understand it you're only bound by the open source terms included with the software at the time you started using it - - basically if you modify the code you're bound to release your changes if you redistribute the software. They cannot change the version you're already using retroactively.
Was the license ever valid though, if the copyright owner didn't issue it? If I stole a car, then signed a contract giving you the car for $1, then would you be able to keep the car?
No, you'd have to give them the car, because the rightful owners are denied a car by you keeping it. But be careful, licensing doesn't fall under traditional ownership/theft rules.
Obligatory IANAL but... Pretty sure possession of stolen property isn't legal even if you paid for it.
If the deal appears to be too good then you can be charged with handling stolen goods, which is a loophole closer for people palming off stolen items to friends for almost nothing. If you pay what is considered a going rate for an item that turns out to be stolen you are most likely not breaking the law, though of course that doesn't mean the property is yours or that you would be compensated for it's removal from your ownership. Note this is relevant to UK law, no idea about other jurisdictions.