Do you have a source with some official statement for that? While that is indeed the case in practice, all I read was to the contrary saying Insiders without genuine licenses get only time-bombed activations. Ah, another question: How would you do a clean install of such an permanently activated installation on a another computer or the "same" one with another mainboard? Do they have a system for those who upgraded to avoid installing their old Windows 7/8 first Insiders might be able to take advantage of?
I did mine Saturday. My parents Tuesday. Mine was legit 8.1 key upgraded. My parents was Daz and 7.my tablet was legit did that and my laptop. All past week. All activated. I just did my inlaws today. Legal update from Ms. Guess what all the keys and build is identically same as insider. All options and all.
There are a lot of existing posts (including official Microsoft blog posts) from before 29 July that say that Insiders won't get a free copy, only time-bombed. I haven't seen any official posts to the contrary. However, since 29 July, the practical situation is different. It may or may not stay this way. You can't.
i upgraded back then before launch date to 10240 and i just did a clean install, activated without having to enter any key, just used my insider hotmail account as user name
Dude the 29th build has insider option right from Ms server. And it says uninstaller preview under update history. Just like the leaks. Were rtm man. And Ms has said it.
I did a clean install of Windows 10 Pro on my new laptop and it activated as soon as I connected to wireless. I also did a clean install of Windows 10 Home on my previous laptop that I've got listed on Kijiji, and it also activated when I connected it to my wireless router. both installs were upgrades from Windows 8.1 ProWMC and Windows 8.1 Core respectively.