Microsoft will give those who tested the next version of Windows through the Windows Insider program a free upgrade
path to Windows 10 when the OS is released to manufacturing, meaning you will be able to upgrade to the final RTM version without the need of a clean install.
When this news was first revealed by Microsoft's Gabriel Aul
through Twitter yesterday, there was a bit of confusion as to how the upgrade would work, with some people speculating that the free upgrade meant a free Windows 10 license, however that is not the case.