Yes, it's legal. Each HW license is for use on one computer at any one time, not per console or audio system.
The assumption that your composite sampleset might tax any PC available is worth questioning before you put in a lot of time and money. Is it surround? How many ranks and how many surround perspectives? How long are the reverb tails?
For comparison, the Nancy sampleset with 65 ranks times 4 perspectives and 6 second reverb (and some two-layer tremmed ranks) runs well on an i9-12900K processor and 128 GB memory with Windows 11, at 96k sample rate and 512 sample buffer and 8192 polyphony limit. Higher polyphony at 48k and 256 buffer. Edited: Buffer sizes were backwards.
Will you use much more than about 250 ranks (including your surround ranks) at full organ? Are the long releases more than 6 seconds? If no to either question, one PC could do the job.
There are bigger CPUs in terms of number of cores and multithread capacity. Ryzen 5950X, for example. But make sure the single thread performance is also high because HW does demand good single core speed as well as taking advantage of lots of cores. The biggest Xeon and AMD CPUs tend to compromise with lower single core speed compared to Intel Core gen 12.