In compiling the major libraries and utilities in NEMO the proper graphics package should be installed too. The $NEMO/src/kernel/yapp directory contains a number of yapp implementations and your need to decide which yapp interface(s) to use.
To test a particular graphics device you can use:
% cd $NEMO/src/kernel/yapp % make yapptest_mongo
where the trailing _mongo part tests, in this case, the mongo device driver.
This usually means that the YAPPLIB environment variable in the startup script $NEMO/NEMORC.local has to be adjusted accordingly.