I have NS-2.34 already installed with olsr patched to it.
Which olsr patch ? ? um-olsr-1.0.tar.gz ?
Please explain why you want to use your current ns-2.34 for GPSR-KeLiu.
( Many of the complex patches will make conflicting changes to the files.)
And : You can have as many versions of ns-allinone-2.xx as you want,
installed at the same time. But do not add any path text to .bashrc.
Also : No problem having lots of different executable 'ns' :
Just rename all 'ns' to different names, like ns-umolsr, ns-gpsr-ke.
Example command : $ ns-umolsr olsr_example.tcl .