Just curious...I know nothing about PCs but my trust laptop runs wonderfully on W7 and I’m wondering what it would mean for me if this proposal was accepted by Microsoft.
It would continue to run. Potentially it could run better over time.
As things stand, Windows 7 will never get any more regular security updates when vulnerabilities are found. Since many of those vulns are also in Windows 10, which _will_ get the patches, it's relatively easy for a Bad Guy to "reverse-engineer" the Windows 10 patch, discover what vulnerability it fixes, and then test to see if that vulnerability existed in Windows 7 also (very likely it does). Then the Bad Guy crafts a new malware exploit to take advantage of it, knowing that there are a tens of millions of Windows 7 machines still in use that will never get patched.
So.... if Win7 were to be open-sourced, -and- the bright-eyed folks who read the source discover the vulnerability, they can design and release a patch for it. In that way -- if you keep up with those patches -- your Win7 computer would be more secure than otherwise.
However, that's a long shot. I wouldn't bet on it.
Just keep your trusty Windows 7 laptop off the internet, or at least be VERY VERY CAREFUL about what sites you visit and what links you click. Windows 7 is now considered UNSAFE FOR INTERNET USE.
For private, off-line use, it's still pretty safe and will remain so for a long time, IMO.