(Some had wondered if Windows Insiders might get the final build earlier than July 29, but the answer seems to be no.)
Windows Insiders will get the "final" release as "just another flight," Aul said. As long as testers are running an Insider preview build and connected via the Microsoft Account they used to register for the program, they will get the final build for free and remain activated. Those who want to clean install on the PC using an ISO will be able to do so, if they want a fresh start, but only after they successfully install the final build and activate it.
Update (June 22): Over the weekend, Microsoft changed the wording of the original blog post to remove the part about remaining activated. (The reason seems to be that company officials don't want to enable those with non-Genuine Windows to be able to get a Genuine copy via the Insider channel.) The final interpretation: As long as users are running an Insiders build on/before July 29 and is upgrading from XP, Vista, Windows 7 or 8 to Windows 10, they will get Windows 10 for free. Those not in the Insiders program will be able to get Windows 10 for the first year it's available for free, but only if they are running Windows 7 or Windows 8.1.
Update No. 2 (June 22): Microsoft has taken another stab at explaining this. And it turns out those who came into the Insiders program from anything other than a Genuine Windows 7 or 8.1 build will NOT be able to get a free copy of Windows 10 RTM once it's available. (They will be able to continue as Windows Insiders and get Insider builds after RTM, however.) The requirement for a valid Windows 7 or 8.1 as a prerequisite for the first-year-free deal for Windows 10 applies to everyone, Insiders and non-Insiders alike. This is my best interpretation of what Microsoft's updated blog post says.
Speaking of Microsoft Account, Insiders who want to continue to get preview builds will need to pair their Windows 10 test machines with Microsoft Accounts as of the next Windows 10 preview release. (Using a Microsoft Account won't be a final requirement for using Windows 10 once it's out, however.)
Microsoft is still not providing a date as to when those who want to upgrade to Windows 10 Enterprise will be able to do so. Those running the Windows 10 Insider Preview Enterprise edition will be downloading and activating it from the Volume Licensing Service Center -- not getting it as a free-for-the-first-year upgrade. Enterprise users will be upgraded to the final release of Windows 10 "through an active Software Assurance agreement," Aul said.
(I've heard August 1 and early September or October as rumored availability dates of Windows 10 Enterprise. But nothing official so far.)
Microsoft is hoping its Insider testers will continue to be part of the Windows Insider program after July 29, officials have said, as the preview program will continue post-RTM. Insiders also will have an option to leave the program.
With the next build of Windows 10 preview for PCs -- which is expected some time in the coming few days -- Microsoft will be uninstalling the Insider Hub to prepare for the final release of Windows 10. But Insiders will be able to reinstall the Hub if they desire, said Aul, with a series of steps. The Insider Hub will be reinstalled again in preview builds that come after July 29. The Feedback app will continue to remain in the preview builds and final release.
Finally, Microsoft is working on "new infrastructure in Windows Update to help us deliver new builds more effectively to Windows Insiders, and ensure that we're flighting builds to people who have registered and opted in to the program," Aul said, without offering further specifics on what that will look like.