opening.bnr is a file related to Wii homebrew development.
It is a normal ARC-file (archive) with an extra header.
The ARC-file contains 3 files:
These .bin-files are compressed using the LZ77 encryption, more information on Wikipedia.
The extra header is very similar (possibly identical?) to the part A of the content.bin file, starting from (and including) the field Zeroes_1, i.e. the second block of part A.