Well, first of all, admittedly "senicOS" is a bit of a mouthful - it's not actually a custom operating system, but simply a yocto based linux distribution.
You can find the sources on github.
The Makefile supports both running locally on a suitable Linux machine that is able to build the OS as well as running the checkout on a non-Linux machine (typically macos or FreeBSD) and control the actual building on a remote host.
To this end the Makefile is currently hard coded to perform these actions on and against a host named osbuild. It then falls into the responsibility of the user to provide a suitable SSH configuration for such host.
To update the host with local (uncommitted changes) run make upload.
You can then perform a build with these settings on the host like so:
source oe/oe-init-build-env
This will use (and create) the default build directory named build, however, you can provide an arbitrary custom name (usually 'your' username) i.e.:
source oe/oe-init-build-env xxx
and then perform a separate build in your own environment.
To download the build, run make download on your local instance, this will (r)sync the server's build directory to the local build directory (in essence as if you had run the build command locally) at build/tmp-glibc/deploy/images/senic-hub-beta/.
First, make sure to get the the device name of the card reader (usually da0) by running camcontrol devlist.
Once downloaded use dd but make sure to provide a sufficiently large blocksize, i.e. 1024k:
sudo dd if=build/tmp-glibc/deploy/images/senic-hub-beta/senic-os-dev-senic-hub-beta.wic of=/dev/da0 bs=1024k
Check the device name of the serial adapter by performing a diff between the contents of ls -a /dev/ before and after plugging in the adapter (usually ttyU0), then use screen (either as root or with sudo!):
sudo screen /dev/ttyU0 115200 -L