Microsoft officially stopped giving free Windows 10 upgrades way back in July 2016. However, they left an easy loophole for anyone who was late to the party but still wanted a free upgrade.
They allowed anyone using their Assistive Technologies to upgrade for free. The Assistive Technologies make computers easier to use for people with disabilities. Some of those tools are Narrator, a screen-reader app that vocalizes text; Magnifier, a digital magnifying glass for those with poor vision; and Speech Recognition, which allows you to control your PC using your voice alone.
Even if you did not need those technologies, Microsoft gave you an easy way to get the Windows 10 update by visiting this page and upgrading their version of Windows.
Now, MS will be sunsetting that option and as per the page free upgrades for those who need assistive technologies will end on December 31st, 2017. (The original extension was due to new assistive technologies not showing up till the July 2016 update.)