As you know, BSB4 charts
are encrypted, and unlocked for a particular PC by a key tied tightly to the individual PC's fingerprint.
The publisher of the BSB4 charts provides a decryption interface for Windows only. Why? I suppose at the time BSB4 was developed and initially released, linux
was a very small player in the PC chart plotter space. Android did not even exist. And now, there seems to be no new development going on in BSB4. Not enough vocal customer demand for alternate interfaces.
It may be possible to obtain the confidential BSB4 API specs from Maptech
under some non-disclosure arrangement. That would enable creation of a BSB4 PlugIn for linux and Mac. Might be worth a query to Maptech