If I buy a Forney welding machine from Amazon, does the warranty still apply?

Yes, the warranty will still apply. The warranty for the welders is 5 years on the transformer, 3 years on the rest of the internal components, and 1 year on the MIG gun, relays, contactors, regulators and accessories. You can see full warranty information here: https://www.forneyind.com/support/warranty-information