If you think that it is a trial, think again.
During the installation process, Windows asks you which copy you want to download, but will never ask for a license. I went through the installation process on a VM, and there is no text box for a license code. None. So twiddle your thumbs while you install a perfectly legal version of that Windows 10 Pro you always wanted, for free. Oh, and I forgot to mention: In the OS menu, you can select a non-Insider build (No N) or an Insider Build (With an N). Remember that when you start typing a mean comment about "He has to use a regular build! He has to use a regular build!". An non-activated version of Windows is not a regular version/build of Windows. That's why they ask for a product key before the installation starts. You get a different OS depending on whether or not you enter a key. A different build. You can try calling me out on this one, but the evidence points to the fact that the Insider Installer is a legal, safe, and easy way to get any copy of Windows 10 for free. A community build that can be run on a workbench computer without the hassle of monthly fees or licenses that are tied to hardware rather than software. Windows 10's version of Windows Buisness Licensing. Oh wait, they have that too. Sadly, it requires monthly fees. Insider Installers don't. Which would you choose? Getting a legal version, or running the risk of going to prison? That should end it.
The very first line of your signature is:
DISCLAIMER: ANYTHING I SAY COULD BE WRONG. DO YOUR OWN RESEARCH!
So I did my research. I found out a ton of info. Most notably, Microsoft includes stuff in the production line, and Insiders don't even know about it. And having your OS shine with untouched features is worse than having partly tested, functioning features that run well on the OS. So, that statement would be incorrect.