There’s no need to change the fee in the client. They only need to adjust the fee in their own process if they build the transaction themselves.
It’s not clear whether they build the transaction themselves.
If they use the sendtoaddress or sendmany RPCs then they don’t have to change the fee. The client will use the current fee. If it’s not then it’s a bug we must fix. Unless they are using a client that is not fully synchronized which means it doesn’t know the current fee.
If they use createrawtransaction or generate the transaction themselves in another way then they need to get the current fee from the paytxfee field of the getinfo RPC and apply it to the transaction they generate. I wrote an example process here:
We use a price per kb like all other coins. But this price per kb is not fixed, shareholders can vote to change it. And it depends on the currency.
Currently on NSR it’s 10 NSR per 1000 bytes, and on NBT it’s 0.05 NBT per 1000 bytes.
To get the fee on a specific unit you must run the getinfo on the RPC server of the right unit:
For NSR it’s nud getinfo or nud -unit=S getinfo. For NBT it’s nud -unit=B getinfo.
If you connect to RPC through HTTP it’s on port 14001 for NSR and 14002 for NBT.