But do you really need new software just for a new layout?

The design is as responsive as is needed. You hit post, your post appears, what else do you want? There's maybe like 3/4 features done in about 12 lines of js that this might need.

Backend reworked, maybe. Updated to not be sql/static html generated every time would be good.

GUI can be updated with a bit of CSS and would blow the pants off of every site out there.

Modern "responsive" design is missing the point, because might as well use something like Disquis, and that is just a pile of garbage.