eSOL is a company based in Japan that Nintendo used for some Wii libraries. They used:
- PrFILE2 (FAT filesystem, used in VFFs)
- PrMAIL (Mail system, not much is known about this)
- PrUSB/Host (USB library)
Nintendo also used their libraries for the Wii U and Switch.
We don't have these libraries, but we found some of the code from PrFILE2 in Nintendo's OSS pack for the Wii U.