@ZacB_ @joebelfiore Yes, as long as running a prerelease build connected with registered MSA: http://t.co/vlaGyfwzbr — Gabriel Aul (@GabeAul) June 21, 2015

To make things even murkier, Microsoft's Gabriel Aul later said that Windows 10 testers would remain activated when the final release arrives, as long as they have associated their Microsoft account to the preview build. We think that means that Insiders who don't have a valid Windows 7/8.1 copy will still get a "legit" copy that can be updated, but not a valid license. In other words, you can keep the free software for personal use, but not for your business. This does jibe with previous Microsoft statements that it would provide a "mechanism" for all users to get a free Windows 10 copy, pirates included.

Assuming that's accurate, it's not clear whether Microsoft has actually changed its upgrade policy or just made an error on the original post. It probably would have saved some confusion if it had included an explanation after changing the wording, instead of just letting the internet read the tea leaves.