the difference is pretty fundamental, because contracts require a meeting of minds and explicit assent. that's why proprietary software that attempts to regulate use has tightly controlled distribution, so that you only get access to the copy after having given up your previously-unlimited rights to run the program.

writing in a license "you shall not run the program for " while distributing the program widely doesn't stick, because the recipient doesn't need any license to run the program.

that's why amateurs who set out to imitate copyleft poorly without understanding the underlying legal mechanisms set themselves up for failure, and end up fooling and hurting others in the process