The Mac versions of the Bidule plugins on this site have until now supported both PowerPC and x86 Macs. This means there was no support for x64 architectures, so unless you were running Bidule in 32 bit mode (see screenshot below), the Bidules were not recognised.
I have now rebuilt the Bidules (both MIT HRTF and Ambisonic ones) for the Mac only, with support for both 32 and 64 bit architectures. However I have dropped support for PowerPC platforms (did anybody still use it?).