In November 2015 OS X 10.11 "El Capitan" introduced the function SIP (System Integrity Protection) designed to improve system security by preventing the editing of files deemed critical. This was the case for unsigned drivers, i.e. non-Apple certificate.
As a result it became mandatory to Disable SIP to install the Prolific drivers, FTDI, or still Keyspan, to identify the navigation devices connected in USB on our Mac (¹).
If MacOS 10.12.0 "Sierra" had disabled the SIP, it comes to be reactivated by the update 10.12.2. But not to worry, the drivers are now signed :
- Prolific PL2303 V.1.6.1 for USB GPS (tested)
- FTDI V.2.3 for multiplexers (tested)
- Keyspan 4.0 for adaptors USB/serial USA-19HS (Not tested ²)
Hence, it is no more necessary to disable SIP.
(¹) See http://www.francis-fustier.fr/gpsnavxhard2.html
(²) Signature of the driver likely but unconfirmed, to test.