Behind the scenes the city council has already started work to switch to Microsoft Exchange to handle email and calendars.
Open-source pioneer Munich has already started work to replace free software with Microsoft products.
While Munich City Council is widely expected to swap back to Windows 10 and other Microsoft software by 2021, the final decision to turn away from open source won't be taken until at least November this year.
However, the council has already begun work to switch to Microsoft Exchange, which will replace the only recently installed open-source groupware Kolab in handling email and calendars, a city council source confirmed to TechRepublic.
"The city will use MS Exchange. It will be used for mail and calendar, so Kolab will not be used anymore," said the source, adding that the switch will take place in November.
According to the source, the decision to use Microsoft Exchange appears to have been taken in Spring this year, shortly after the council decided to investigate the cost of switching back to Windows.
Matthias Kirschner, president of the Free Software Foundation Europe (FSFE), said he has also seen evidence that Munich City Council has started work to use Exchange to handle emails and calendars--backing up a report by German IT site Heise.
He said that evidence reinforced information he had received that Munich has begun switching away from using the open-source Kolab, which the council had chosen to handle mail, calendars, tasks, and contact lists. Kolab was installed as part of a wider four-year project that was only recently completed, finishing in January this year, and that cost several million euros.
The move to Exchange will mark a significant shift for an authority seen as a champion of open-source software. Munich spent nine years and millions of euros shifting some 15,000 staff to a Linux-based OS and other open-source software, and attracted widespread coverage as one of the most high profile examples of a large organization moving away from Microsoft.
News about Munich's move to Exchange have also reached Günther Meyer, co- chairperson of the Pirate Party in Munich, who says it will precede a wider shift back to Microsoft software.
"They have already been working on Exchange for some months. A migration to Outlook will start in the near future," he said.
A spokesman for Munich city council said it was unable to comment on whether the organization had begun the move to Exchange, citing security concerns over revealing information about such "software components", despite the council having previously openly discussed its plans to use Kolab.
While Munich has always run a minority of Windows machines and other Microsoft software and services, the council's previous philosophy was to use free software wherever possible.
However, today there is support among the city's ruling SPD-CSU coalition for phasing out the use of open-source software, and the council took the first step back towards Windows 10 earlier this year.
Munich's administration is investigating how long it would take and how much it would cost to build a Windows 10 client for use by the city's employees. Once this work is complete, the council will vote again in November on whether this Windows client should replace LiMux, a custom version of the Linux-based OS Ubuntu, across the authority from 2021.
The FSFE's Kirschner said that any switch to Exchange should not take place without the council's explicit approval.
Kirschner said that councillors had agreed in February to hold off on any actions to scale back the use of open-source software until the costs of doing so were known.
"It was agreed that the final decision will be made by the city council members after they receive a calculation of the costs," he said.
The Pirate Party's Meyer highlighted findings by consultants Accenture that most of the problems with IT at the Munich stem not from the use of open-source software, but from inefficiencies in how Munich co-ordinates the efforts of IT teams scattered throughout different departments.
Microsoft did not respond to a request for comment.
It also emerged this week that the LiMux section of the city council's website had been removed last year. A spokesperson for the council said the section was not carried over to a new version of the site after a redesign because the migration to LiMux had been completed in 2013.
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