If this is non-nil, the delivered application is not saved, but run in memory instead.
This can be useful while still deciding on the best delivery parameters for your application. Writing the delivered image to disk takes a lot of time, and is not really necessary until you have finished work on delivering it.
Note:
When using this keyword, the deliver function still demands that you pass it a filename. However, the filename you give is ignored. You can use nil.
LispWorks Delivery User Guide - 10 Aug 2017