Its a shame the article "wont go into details" because it is only the details that are interesting. The rest is known. Tim Patersons wikipedia page mentions he

Its a shame the article "wont go into details" because it is only the details that are interesting. The rest is known. Tim Patersons wikipedia page mentions he had access to CP/M source and copied at least the "API" for compatibility purposes. Considering this is low level assembler, for 2 fairly small, mininmal operating systems, basically handling interrupts and interacting with the bios etc, even if Paterson didn't have access to the source, (but may have had e.g. read the same books as Kildall) two operating systems will have similarities, especially if they share an API. There are only a couple of ways to set up an interrupt handler, or call a bios function.