SAMBA is a free implementation of the SMB protocol, used by Windows
(yes, the Microsoft OSs) for disk file sharing. It gives much the same
sort of sharing Pathworks does, over about any TCP/IP, and the VMS
version here can be used to make VMS volumes available to anything
that speaks SMB. Samba is getting updated regularly, and shortly should
be able to handle full authentication by the latest Microsoft protocols.

A client which works a lot like "tar" is available also. In addition,
Linux has a "SMB file system" which lets other systems just access
Windows disks as if local. A "smbtar" exists which will allow VMS
to back up Windows volumes also.