If game client let you cancel spellcast and cast another spell immediately but this information is not sent to server because game locks another spellcast untill server confirms that previous spellcast is finished then is a bug. And according to nampower description this tool should fix it (in computer memory not by modifying client files). I can confirm that when you start casting a spell and cancel it there is window of time that will prevent you from using another spell (2*latency time).
If im not mistaken current spellcast works like this:
Non instant spellcast start, client sent info to server [+latency time], player canceled spellcast, client sent cancel info to server [+latency time], /player could not cast another spell for ^latency time from client to server^/, server recieved spellcast cancel and sent „spellcast finished” confirmation to client, /player could not cast another spell for ^latency time from server to client^/, client recived confirmation that previous spellcast is done and can cast another spell
With nampower c-s communication should work this way:
Non instant spellcast start, client sent info to server [+latency time], player canceled spellcast, client sent cancel info to server [+latency time], player started casting another spell using nampower fix, nampower fix sent info to server through client, server recieved previous spellcast cancel and sent „spellcast finished” confirmation to client, server recieved another spellcast info through nampower fix, client recieved confirmation that previous spellcast is done and can cast another spell
At Least in theory since I have never tested nampower so far.
Pity this was not fixed before BC.