CentOS is being used by a lot of HPC shops, academia and research units like one where I administer a HPC.
For the number of cores that HPC shops run, the bill would become FAT real soon if we have to pay for OS. I'd imagine that if IBM messed with CentOS, it'd be called out for being incredibly dumb about RH business, and there would emerge an open fork of RHEL that is not owned by IBM like CentOS is.
To give you an idea, we run CentOS 7.5 on all compute nodes, but make use of paid for RHEL for our identity server, DB servers and the like. If IBM touches CentOS, the whole domino falls and we start looking for alternatives.
For the number of cores that HPC shops run, the bill would become FAT real soon if we have to pay for OS. I'd imagine that if IBM messed with CentOS, it'd be called out for being incredibly dumb about RH business, and there would emerge an open fork of RHEL that is not owned by IBM like CentOS is.
To give you an idea, we run CentOS 7.5 on all compute nodes, but make use of paid for RHEL for our identity server, DB servers and the like. If IBM touches CentOS, the whole domino falls and we start looking for alternatives.