These archives contain no game data. They contain BoktaiBuilder, which
compiles the game locally from your own legally dumped ROM and GBA BIOS.
Steam Deck: install BoktaiBuilder.flatpak in Desktop Mode with
flatpak install ./BoktaiBuilder.flatpak, then launch it from the app
menu or add BoktaiBuilder as a Non-Steam Game.
Desktop Linux/macOS: extract the matching tarball and run BoktaiBuilder.