Emacs. I mean the user base and the scope is kind-of limited, but it's really easy to build thin-clients and some certain types of applications in Elisp. And

Emacs. I mean the user base and the scope is kind-of limited, but it's really easy to build thin-clients and some certain types of applications in Elisp. And against all prejudice, modern Elisp is quite a pleasurable language to write in. Furthermore, it's a joy to use that sort of "apps" in emacs and the community really likes it when those pop up. Also, there already are rather featureful apps like Gnus, Magit, EMMS and Elfeed, and the user is allowed vast customisation even without you really thinking about allowing it (advices, monkey-patching, keybindings, hooks, etc.). P.S.: While I don't suggest this as seriously as those who suggest Qt and WxWidgets et al., if your demographic is hackers, you can consider it.