I have debian operating system and software repository.
I would like to emulate or simulate on my computer,
some verilog code from opencores.org. Especially the processors.

Can this be done? What opencores project do you suggest I use?
What software should I use? Here are two related packages in debian.

iverilog is a compiler that translates Verilog source code into executable programs for simulation. The currently supported target is vvp for simulation.

Verilator Converts synthesizable Verilog code into C++.
It is not a complete simulator, just a compiler.