Installing GNU parallel without root permission
./configure --prefix=<target>This will make the installation in <target>/bin, <target>/lib etc.; just do the make install as usual.
Choose a <target> you have access to (something in ${HOME} if need be), and adjust your PATH to include <target>/bin (and, perhaps, MANPATH to include <target>/share/man so you get access to the man pages as well).
If you have conda, conda install -c conda-forge parallel is also a one-line solution.