<i>Tom's Hardware theorizes that if Apple were to adopt the open-source instruction set of RISC-V, it may save the company money because it wouldn't need to pay Arm a license fee for its instruction set.</i><p>The money Apple pays ARM is insignificant.<p>More likely in my opinion, they are exploring RISC-V as a base from which to build their own proprietary chips. There is nothing "open" about Apple.
It's confusing that RISC-V is so often described as "open source". The specs (ISA + extensions) are open and free from patents (at least as far as we know). While there are a large number of open source implementations available, many of these, however, implement only a simple microcontroller-style RV32I core.<p>The cores available in "large" physical chips you can buy today (XuanTie C906 on the Allwinner D1 SoC, SiFive U54/74 e.g. on the BeagleV and HiFive Unmatched) are proprietary. I think one of the few companies that open sourced their commercially used cores is Western Digital ("swerv" cores - <a href="https://github.com/westerndigitalcorporation/swerv_eh1" rel="nofollow">https://github.com/westerndigitalcorporation/swerv_eh1</a>), but these are also RV32I microcontroller-class CPUs.