Computer Industry slang for a
contractor. An IT contractor will
work for anyone, provided they happen to be
the highest bidder. Contractors don't get
sick pay, they don't get
paid holidays, they don't get
medical benefits,
life insurance or a company
pension.
No company car, no complimentary membership of the local health club, they are not employees but rather self employed and can be fired at a moment's notice at any time.
The only benefit they get is their salary. And, just to add to the metaphor, most contractors get paid by the hour.