similar to: import rhinoscriptsyntax as rs
is there something similar to: import kangaroo
is there an option to do something like that or do you need to rewrite components to have that functionality?
generative modeling for Rhino
if the add-on .gha you would like to reference exports some functionality, you should be able to import clr and then use the normal clr.AddReference and similar methods (you could try also with clr.AddReferenceToFileAndPath) to load it. There are some examples of this online.
Then, again if there are public class to use, you should be able to import the add-on namespaces and do things with them.
I hope this helps,