To be able to load the BioTop bridge (and ICF file) into Protege, the following OWL files should be put in the same directory:

Observables examples in OWL - nested model
https://csfe.aceworkspace.net/sf/go/doc3715?nav=1

New BioTop version
https://csfe.aceworkspace.net/sf/go/doc3920?nav=1

The ICF examples also needs the BioTop bridge OWL file.