There are a number of ways in which SP can manage competing keyset designs, especially when a design seeks to copy a previous one in some obvious fashion. They can simply reject the copycat design outright. In fact, I suspect that is exactly what most of this community expects them to do. Alternatively, they can accept the design but with a heavy premium.
The former action shuts down on such copycat designs completely. The latter gives these designs a chance, and the premium then serves dual purposes: to discourage interest (in the hopes of seeing the copycat die in IC), or to provide the financial means to compensate the original designer (in the case where enough people with too much money still agree to buy in).
All of this is merely a consequence of SP having control over how the "IP rights" of designers are honored, given the fact that there is no formal IP law that will step in and do it for them. It is also a consequence of SP being the only game in town for spherical keycaps. It could be worse: they could have decided to just get out of the custom keyset business all together, focusing exclusively on their large industrial contracts instead.
