Open source developers who contribute to OpenOffice should stop donating their code to Sun Microsystems, open source advocate Bruce Perens has urged.

The executive director of the Desktop Linux Consortium made his call after details of an April 2004 deal between Sun and Microsoft emerged in a recent Securities and Exchange Commission filing.

The deal involved, among other things, the two companies promising not to sue each other over past patent infringement claims. But according to legal filings this protection does not extend to OpenOffice, the open source office package.

OpenOffice includes applications for word processing, spreadsheets and presentations. Sun acquired the product in 1999 and in 2000 released the source code under an open source licence.

Perens told vnunet.com: "I would counsel [developers] to stop assigning the copyrights of their modifications to Sun and keep them under their own names, licensed under the General Public Licence and in the open version only."

Describing the legal arrangement between Sun and Microsoft as "creepy", Perens added: "It essentially says that Sun will not stand together with the open source developers who contributed to their own product."

But Sun spokesman Russ Castronovo said : "He [Perens] can make whatever call he wants to make. There is no change in the protection being offered to the OpenOffice users."