Looks like part of the attempt in mid-to-late 1980s to revive the magic technology of ejector lift augmentation, which also led to the General Dynamics E-7 and the construction and testing (at Ames) of a large powered model thereof.
Fortunately someone rammed a big wooden stake through its heart...
The second broad variant of the Pegasus approach (under investigation by
de Havilland of Canada) is to augment the thrust of the forward nozzles by using ejectors located in
the fuselage (Fig. 4). This has the advantage of retaining the cold front exhausts (thus a voiding the adverse effects of hot gas ingestion) and providing a relatively low impingement velocity on the ground plane. The two rear hot nozzles are again combined into a single nozzle as in the previous discussion.
Uncertainties that remain to be resolved include (a) the extent to which thrust can be improved
by cold flow augmentation within the geometrical constraints of a practical supersonic aircraft
design, and (b) the effect of the fountain caused by the impingement of exhaust flows (in this
case heating effects should not be a problem due to extensive use of cold air; however, the
fountain may cause upset moments on the wing and fuselage).
I did not read through the whole report, but IMHO, although De Havilland Canada may have studied this I doubt if it was a real project. I think we should distinguish here between study drawings and projects, the former just to illustrate some scientific/engineering points, the other to aim towards actual hardware. A thin dividing line, but I think we should recognise that.