The whole upgrading to Windows 10 from a non-genuine Windows is so confusing. First, Microsoft announces that it plans to give Windows 10 as a free upgrade regardless of whether users don’t have a genuine copy of Windows 8.1 or 7. Then shortly afterwards, Microsoft backtracked what it said and told everyone that pirates will not get Windows 10 for free.
Quite a few people have reported on Reddit have reported that they have successfully upgraded their pirated copies of Windows (check out this thread and this one), both 8.1 and 7, to Windows 10. Surprisingly, many of these people got their Windows 10 activated, despite their previous Windows installation not activated.
Many users are claiming that all they had to do was run the Get Windows 10 app and then the magic began. They didn't even need to run any hacks or exploits.
However, some users have also reported that their Windows 10 upgrade did not activate from a non-genuine copy of Windows. So users who don't have a genuine copy of Windows who try to Windows 10 shouldn't be surprised if their Windows 10 machine didn't activate. If you run across this problem, then it's probably best you purchase a copy of Windows 10 if you can afford it. Or enroll in the Insider Preview, where Microsoft keeps a close eye on what you do, and how you use the OS, for product improvement purposes, of course.