I’m the author of Siilihai web forum reader. I just released a new version which can read Discourse forums using it’s API. You might want to check it out. Posting support is still missing, but it should be doable.
For developers this gives a Qt/C++ interface to access Discourse (and other) forums. It might be useful for some other applications as well. All code is available at Github.
The official release posting is here Siilihai News: Siilihai 2.5.0 released