Version 2.9.1 of the RealSense SDK has now changed from 'pre-release' status (where it was still having some work done on it) to stable 'latest release'. This build lists Mac OS (High Sierra 10.13.2) under the Supported Platforms for the first time.
A new dependency package libudev-dev was added in 2.9.0 to the installation for Linux OS due to a custom libusb library that was employed in this release. Migration from previous versions requires sudo apt-get install libudev-dev
Details of other new features, examples, bug fixes and Known Issues can be read in the Release Notes. The Unity wrapper is not in this version but that and Matlab support are the final remaining items on the current to-do list of upcoming features, so the developers are to be congratulated for their hard work in progressing the SDK.