Or, it might be an alien spaceship after all?

There's an abstract up at Nature about that interstellar visitor of last year, with the tantalising title:

Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua')
 
Here's the key part:

Here we report the detection, at 30σ significance, of non-gravitational acceleration in the motion of ‘Oumuamua. We analyse imaging data from extensive observations by ground-based and orbiting facilities. This analysis rules out systematic biases and shows that all astrometric data can be described once a non-gravitational component representing a heliocentric radial acceleration proportional to r⁻² or r⁻¹ (where r is the heliocentric distance) is included in the model. After ruling out solar-radiation pressure, drag- and friction-like forces, interaction with solar wind for a highly magnetized object, and geometric effects originating from ‘Oumuamua potentially being composed of several spatially separated bodies or having a pronounced offset between its photocentre and centre of mass, we find comet-like outgassing to be a physically viable explanation, provided that ‘Oumuamua has thermal properties similar to comets.

I know it's a long shot, but I guess it still leaves it open that it was an alien spaceship venting or trying to accelerate?