The KunaiGC is as an IPL-Replacement for the Gamecube.

But what is the IPL and why do one want to replace it?
IPL stands for (I)nitial (P)rogram (L)oader and it is the first program the Gamecube starts on it's bootup.
With an IPL replacement we can decide what the Gamecube starts on bootup. This could be Swiss or any other .dol-File.

How does KunaiGC does all of that?
With an KunaiGC installed the Gamecube asks the KunaiGC what to do:

• If the KunaiGC is active the KunaiGC loads it's contents from it's Flash e.g. Swiss directly.
• If the KunaiGC is inactive the KunaiGC is turned of and the stock Gamecube IPL is used.