My understanding is that Apple has a perpetual license. I do not know if that covers only the ARM designs at the time of the signing or anything in the future.
At worst it would seem to be something like Apple has a perpetual license to the arm32 and arm64 instruction sets. They would seem have a license to whatever reference designs ARM was offering at the time. So on day zero they have working hardware. However for every day since then they have been able to update or replace elements of that design, while maintaining instruction set compatibility. The M1 is the results of that process after many years.
Various other companies have done similar things. For example we have the Broadcom ARM cpus in the Raspberry Pi and the Qualcomm ARM cpus in various non-Apple phones and tablets. Apple seems to have quite a lead over these two.
Now enter NVIDIA, a company that may be more competitive with Apple than the others with respect to design due to relevant experience and money.