This article is based on the false premise that Windows 10 is currently completely free. It is not. It is, right now, as of this post and for quite some time before, being sold in both OEM and Retail copies on virtually any tech related retailer, both online and brick and mortar.
It is only free if you have Windows 7, 8, or 8.1. If you were still on XP or Vista for whatever reason, you have no choice but to buy it, or find a copy of Win 7/8.1 to buy and upgrade that.
There is no way Microsoft wants a scenario whereby people are still buying Windows 7 / 8 / 8.1 copies floating around to upgrade, because that offers them the choice of keeping an older OS.
What is more likely is that either the free period will be extended, or that the price will drop, or some combination thereof.
uBlock Origin has no such problem and is the replacement for the defunct Adblock Edge. I suggest upgrading if you are still using Edge, worse, Adblock Plus.