Dolphin is the premiere GameCube emulator. It is open source and runs under many operating systems.
Dolphin supports netplay for online multiplayer.
Dolphin can also load up to 4 GBA cores to seamlessly emulate GBA linked games, and is compatible with netplay. It can also link with a select few external GBA emulators
GameCube Optical disks are notoriously difficult to read with conventional hardware, often requiring a specific DVD drive being used in conjunction with aftermarket firmware and software. A modified Wii is perhaps the easiest way to read disks to create backup media.