Please tag the question as Neurorobotics, otherwise a lot fewer people will see your question.
The NRP installation currently compiles nest without libneurosim, yes. So far, we did not experience any problems with that. However, you are of course free to compile nest yourself. All the tools required for that are already installed (as part of the NRP installation process).
The installation script for nest we use is the following:
pip install Cython==0.23.4 mpi4py==2.0.0
mkdir build && cd build
cmake -DCMAKE_INSTALL_PREFIX:PATH=$HOME/.local \
-Dwith-gsl=ON -Dwith-mpi=ON -Dwith-music=ON \
# optional: install UGR's Cerebellum model plugin
mkdir build && cd build && cmake .. && make && make install
cd ../../../../build/ && cmake -DCMAKE_INSTALL_PREFIX:PATH=$HOME/.local \
-Dwith-gsl=ON -Dwith-mpi=ON -Dwith-music=ON -Dexternal-modules=cerebellum \
# check that nest is linked with cerebellum:
# should list libcerebellummodule.so
# deactivate the virtual env from #4
In this install routine, you can simply add a parameter to provide a path to libneurosim.