The transfer-software for HiMD under MacOS-X supports the following MD-Walkman:

MZ- RH1/DH10P/RH10/RH910/RH710

and can be downloaded here:

http://support.sony-europe.com/dna/downloads/downloads.aspx?l=en&f=MT

This software could help developing a Linux-software by analyzing the code of the transfer-program which is only about 1,5 Mbytes in binary. One attempt could be stripping down the binary to X86-code only with http://www.xslimmer.com/ and then disassemble with a X86-disassembler for Windows like IDA Pro.

It appears that only the binary "HiMD Music Transfer" itself is necessary to communicate with the HiMD-Walkman, so the code to be analyzed is very few. The additional program "HiMD Monitor" is obviuously only necessary to monitor whether a HiMD-Walkman is connected to the Mac and create a shortcut-link on the desktop to the transfer program once the walkm an is connected.