I made the mistake of assuming that the license situation would be like Mac or PC apps that run under MacOS or Windows, respectively.That would depend, they actually might be. Read through the license statement for BusyBox and other programs in there. Make sure you're in the right section, not the section for non-profit-non commercial. And not the general GPL V2, go to BusyBox's site.
Most likely, they are required to be open source.
So I stand corrected. But I doubt if Amiko will comply with the BusyBox license and release the source. The 'main.exe' and 'main_so.exe' are 32-bit ARM executables in the 'ELF' format which is supported by BusyBox.
You can disassemble the two programs mentioned above using the Ada disassembler. There is a free demo version of Ada. To view the symbols I used a hexadecimal file dump utility.