10 May 2002 Software giant Microsoft has been accused of trying to stifle the development of open source software by introducing anti-general public licence (GPL) clauses in its Common Internet File Sharing (CIFS) protocol documentation.

CIFS specifies how PCs running Windows can share files with servers and other PCs. The protocol is used by the popular open source Samba product to enable Linux-based servers to run networks of Windows-based machines.

But Samba developers say that Microsoft is forcing them to sign agreements that bar them from using the information in GPL-based products, a move they say will hit the development of Samba. Users of Samba include IBM, Hewlett-Packard and storage vendor Quantum.

When CIFS was released in 1996, Microsoft was keen to make it as open as possible in a bid to win server market share from rivals such as Sun Microsystems. Now, Microsoft is trying to use its ownership of two patents key to CIFS in a bid to restrict its use.

Samba developers say that the new document adds nothing to public knowledge of the CIFS protocol. In any case, the two patents are not applicable to Unix and Linux-based machines. But Microsoft’s aggressive approach could have implications when the documentation is updated to take account of Windows XP and Windows 2000 in August 2002.