Jupyter definitely hasn't lost interest - the IPython team is currently spending a lot of time finishing up IPython 3.0 and seeking funding (grants, etc.). IPython 3.0 is due to be released soon now (3.0 beta 1 was tagged a few days ago, and the development is somewhat in a soft freeze in preparation for 3.0). The general plan is to split up the IPython repo and transition to a Jupyter repo after 3.0 is released, and have a relatively quick iteration to 4.0 (mainly consisting of the repo split).