What constitutes aiding or abetting and/or harboring a fugitive?
The criminal statutes of most states are pretty uniform as what consititutes the crime of "aiding, abetting or harboring a fugitive."
In general, one who knowingly assists, aids, gives shelter, hides, secretes, provides clothing, food, or anything of value to a person known to have committed or suspected of committing a crime violates many states' statutes on the subject you inquire about.
Depending upon the crime committed by the person assisted by the person harboring the fugitive, the person who assisted could be found guilty of a felony as opposed to a misdemeanor. Misdemeanor convictions in most states are up to a year in jail and/or a $1,000 fine. Felony convictions for a particular crime impose a much harsher penalty.