Crankless linear motors are not new, but haven’t been very successful historically. Not only are they more difficult to engineer than crankshaft engines, they also haven’t generally been as useful because what we’ve needed has usually been rotating forces, like for example to drive wheels and generators.
But Toyota has wedded the linear motor with a linear generator that reminds me of the (awful, don’t buy one) shake-light and adapted it to power generation for series hybrid vehicles, where it makes a suprising amount of sense.
A series hybrid is one where only the electric motor ever powers the wheels directly; the fuel-burning engine runs a generator to provide electricity rather than motive power. A parallel hybrid is one where the fueled engine and the electric motor are both always driving the wheels. The Prius is neither, which is why the Prius was such a gamechanger for hybrid vehicle technology.
Other researchers have noted the ability of modern fuel injection systems to compensate for most of the traditional problems of crankless linear engines, and built multi-fuel versions.