There is no such thing as a Felony 4 in Pennsylvania. There are only three degrees of felony 1,2 & 3. Perhaps it is a charge that South Carolina has bought against him. I think there is something missing from the facts that your friend gave you. If he is charged in PA he needs to consult with a qualified PA criminal defense attorney soon.
On the criminal complaint form the police have been using since Dec 2007, there is a box labeled "NCIC Extradition Code Type". NCIC is the national criminal record database.
"4-Felony No Ext" is a code in on the criminal complaint telling the crime computer that your friend is charged with a felony, but the DA does not want to extradite him. This is one of the boxes the police check when filing the complaint. Other options are "full extradition" or extradition surrounding states only.
The charge will stay open and it will be in the computer until he comes to PA or the DA changes his mind and decides to extradite.