A (typically .avastlic extension) is the official method Avast uses to activate a paid subscription. When you purchase a license, Avast sends this file or a 25-character activation key. The license is tied to your email, installation date, and device count.
The internet’s gray market will always promise eternal software licenses—from Windows 10 “lifetime activation” to Avast Pro till 2050. But as cybersecurity expert Brian Krebs famously said, “If you don’t pay for the product, you are the product.” avast pro antivirus license file till 2050