I have seen double articulated buses in the Netherlands some 15 or more years ago. If I remember correctly, they were made by vanHool, and definitely diesel vehicles.

VanHool has double articulated trolleybuses in operation, and Hess has built close to 100 units for various cities in Switzerland (known as SwissTrolley Longo, or LighTram (I think that's their official brand name)). A key feature of these buses is that axles 3 and 4 are steered, and follow quite well in the track of axle 2, which allows the vehicle to handle rather tight curves.

@Goober: These double articulated trolleybuses have axles 3 and 4 driven (two axle drives have been standard for articulated trolleybuses in Switzerland for at least 30 years; the first one was the SwissTrolley, based on a Mercedes Benz O405G, using electrical equipment from ABB.

FWIW, if I remember correctly, it was already Adtranz which sold the trolleybus drive business to Kiepe, if not, then it happened after the takeover by Bombardier.