The concept was more or less invented as a cottage industry and then taken over by the major manufacturers. The market is now dominated by Cat, John Deere, and Timberjack, though neither Cat nor John Deere were in the business early on. The new Morgan Silva Track features information on a new technology skidder with many new features designed to make it ecologically friendly. Among the largest rubber tired skidders ever produced in the world, the Morgan Silva Track combines steerable axles with an articulated frame and hydrostatic drive to make a machine capable of tremendous capacity. Two completely isolated hydraulic systems are provided, one for the drive and the other for the traditional hydraulic functions.
Speed is controlled via variable displacement pumps.
Read here about the problems with rubber tired log loaders as well and their benefits as compared to a tracked loader. The narrative is extensive but there are pictures as well. Nothing like it has ever been made before or is likely to be made again. Hydraulic machines displaced the cable machines in the 1960's. Prior to that time, the heel boom with either tongs or a grapple was the standard.