The reactive house - a term meant to invite comparison with passive house (passivhaus) - is autonomous (in roughly the sense described by Brenda and Robert Vale in their 1975 treatise on the same): the only 'grid' connection it possesses is to the information grid.
The Vale's definition: "A house operating independently of any inputs except those of its immediate environment" roughly captures our intuition of 'off-grid' and seems to embody an idea of self-sufficiency in home design. But the relationship between grid isolation and sustainability is not at all obvious - in fact there appears to be no direct (positive) correlation, possibly the reverse.
First, what counts as an input seems suspect: it would presumably include resources entering the house in permanently connected wires and pipes (electricity, gas, water, sewer), but not resources carried or delivered (wood for the stove, bottles of propane, etc), yet surely this is an irrelevant detail from the perspective of ecological impact. Second, and more important, local production and use of resources might be vastly less efficient, clean, etc than equivalents obtained 'from the grid'. A good example is roof-top solar generation of electricity: using the grid as a 'bank' allows an individual house to have a much smaller number of panels and equipment and remain 'net-zero', therefore greatly lowering the cost and environmental impact of the local installation.
So why autonomous? Primarily, it is a way to force design to understand and account for all costs, externalities and side-effects locally - and therefore more visibly. It is like the difference between living on credit and cash: the latter will not allow living beyond our means, and force us to consider the benefit of each dollar we spend. An autonomous house is a measurable house. We will try to ensure - through observing other reactive principles - that autonomy is not acheived with a net cost to sustainability.
Another implication often drawn from 'autonomous' or 'off-grid' designs is what we can call the noachian (or perhaps 'survivalist') principle: an autonomous house must always be able to function adequately without any external support or dependency - like life on Noah's ark. The reactive house disavows this: circumstances may arise in which a reactive house ceases to be comfortable or habitable due to external factors, and avoidance of such situations at any cost is not a design goal.