Apple Possibly Exploring Open-Source Alternative to ARM Architecture
macrumors.comTom'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.
The money Apple pays ARM is insignificant.
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.
The money will go where the innovative flywheel is. Both ARM and Apple have indulged in expensive wall and glass architecture which is not core to their being in business. Apple has an open source page.
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.
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 - https://github.com/westerndigitalcorporation/swerv_eh1), but these are also RV32I microcontroller-class CPUs.