No. Microsoft never offered free keys for Windows 7 Professional. Any key you find online that works is either stolen (from a leaked OEM batch) or generated fraudulently. Using it violates the license.
Since Microsoft ended official sales of Windows 7 in 2013, obtaining a genuine key is more difficult but possible through official channels: windows 7 professional 32 bit product key generator
Retail (not OEM) licenses for Windows 7 can be legally transferred. You can buy a used retail key from reputable marketplaces, but be cautious. Ensure the seller provides the physical COA sticker or original documentation. windows 7 professional 32 bit product key generator