The city of Munich has hit back at Microsoft in a row over whether the city's plan to use open-source software is cheaper than using Microsoft's products.

The city is currently migrating 13,000 computers from Windows NT 4 and Microsoft Office 97 to a custom build of Ubuntu and OpenOffice as part of its 'LiMux' project. A further 2,000 computers will stay on Windows but are being switched to OpenOffice. The move began in 2004 and will be completed in the autumn of this year.

Last year Munich released figures that it said demonstrated the project would save the authority more than €10m by sidestepping the need to license Windows 7 and newer versions of Microsoft Office, as well as associated hardware upgrades.

In total the LiMux project would cost €23m, compared to the €34m the authority estimated it would have cost to stick with Windows and MS Office.

Munich's figures were challenged in a study produced by HP for Microsoft, which claimed the LiMux project would cost €60.6m, considerably more than claimed by the authority. In comparison, the report claimed, migrating to Windows XP and Microsoft Office would have cost only €17m.

Flawed assumptions?

However the costs in the Microsoft/HP report are based on several flawed assumptions, said Stefan Hauf, head of the press office at the City of Munich.

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Hauf said the HP study assumes support costs for 12,000 clients running the LiMux OS, Munich's custom build of Ubuntu, since 2003. However the number of clients running LiMux in that period has been far lower, as migration has been taking place gradually since 2004, and will only reach 13,000 this year. He added that the report also overestimated the number of IT staff working on the project by putting it at 1,000, which is the total number of IT staff working for Munich.

The cost of porting other business applications used by the authority to Linux, estimated by Microsoft to run to tens of millions of euros, is also exaggerated, said Hauf, as it fails to acknowledge the extent to which web-based apps can be used on LiMux without significant modification.

The way the study characterises the relative hardware costs of LiMux versus Windows is also inaccurate, he said. By comparing LiMux, which is based on Ubuntu 10.04, with Windows XP, the study is not comparing like with like, as its functionality is closer to Windows 7. Consequently the hardware requirements for LiMux relative to Windows 7 should be used, not LiMux versus XP, as is laid out in the study.

On the basis of the present text of the HP study Hauf said it "cannot be regarded as scientific".

A spokesman for Microsoft said: "The study is reliable from our perspective and backed by numerous sources. The City of Munich will be provided a summary of the study. Moreover, we are available to the City of Munich anytime for talks to discuss the study findings in detail."