Worries over total cost of ownership rather than growing uncertainty over patent disputes may have formed the main reasons for the city of Munich's decision to defer its high-profile migration to Linux on the desktop, industry experts have speculated.

Concern over EU patents directives was not Munich's primary motivation in freezing its migration of 14,000 desktops from the Windows operating system to an open source offering based on Linux, believes Gartner vice president Andrea Di Maio.

"Legal risks mostly come from US patents, and no vendor with relevant patents seems to have shown any interest in threatening or initiating a lawsuit," said Di Maio in a statement.

"Instead, the patenting issue may have suggested to Munich that it underestimated costs and risks when calculating the total cost of ownership for LiMux."

Gartner added that a recent study by the city of Vienna had been less favourable to migration.

"Both these factors more likely influenced Munich's decision. The EU directive will have no short-term impact on Munich's implementation of LiMux, because it will not go into effect retroactively," said Di Maio.

Munich's mayor has insisted that the project will continue. And while members of the opposition CSU party have questioned whether Linux would really be cheaper than Microsoft, their doubts have been dismissed by insiders.

In the EU, software patents are not currently allowed, but the Patent Law: Patentability Of Computer-Implemented Inventions Directive may introduce them.

The directive, not yet in final form, is receiving its second reading by the European Parliament. Munich has called for concerted opposition to the proposed directive by interested municipalities and enterprises.