If the tree was cut in October or November and split to staves immediately, the wood will be "partially air dried" at best - probably closer to green. A moisture meter only works on freshly exposed wood, since it will measure the MC at the surface of the pins, as has been explained by Pat. I don't depend on a moisture meter, nor would I recommend it. A rough stave of osage WILL take about one full year to dry. If you rough it out to near bow dimensions, the wood will be dry in three months or so.
In any case, if wood has been over dried, there is absolutely no need to worry. You can simply raise the moisture content of the wood by placing it in an environment with higher humidity and/or lower temperature for several weeks. But like I said; your wood will not be too dry.