T'Kelans, Cainites, Baburites and Shenna for pragmatic, not academic, reasons.
Van Rijn, Adzel and Thea Beldaniel must travel together to a rendezvous with Beldaniel's masters, the Shenna. Neither van Rijn nor Beldaniel wants to travel in a ship owned, pre-prepared or controlled by the other so:
"...they settled on jointly ordering a new-built vessel from a nonhuman yard - there happened to be one that had just completed her shakedown cruise and was advertising for buyers - with an entire supply stock. They boarded immediately upon Solar System delivery..." (David Falkayn: Star Trader, p. 523)
Beldaniel instructs the robopilot with coordinates as soon as they go hyper. The two human beings and one Wodenite are merely passengers in a spacious vessel with staterooms, passages, a galley and a bridge. In this nonhuman-built ship, one compartment is encircled by a transparent strip showing the stars. The ship lands on Dathyna where its drive unit is removed. When van Rijn and his trader team escape from Dathyna in Muddlin' Through, they bombard the castle and the Dathynan spacecraft parked beside it. Since the disabled ship is there as well, it is probably damaged. In any case, it has been bought, has made a single voyage and has then been abandoned but it was a sound investment for van Rijn.