The problem with point 1 is where to stop? Well parallel is written using Perl, so cite that? I have some bash and python scripts. Cite them? The Linux kernel?

The problem with point 1 is where to stop? Well parallel is written using Perl, so cite that? I have some bash and python scripts. Cite them? The Linux kernel? Systemd? I would cite parallel if it is required for the reader to understand or reproduce my research (for example, I report timings which were sped up by parallelisation). Otherwise it's just a tool, Like bash, the C standard library or the Linux kernel. Point 2, the author is giving the code two contradictory licences. I'm not sure which applies. Do I get to choose or does he? I'm not a lawyer.