[coldtea]

I don't think that's all of it (simple payola). While that might have been involved, as it says:

The Second (deputy) Mayor of Munich, Josef Schmid, said the re-examination is necessary because of complaints from employees, who Schmid said are “suffering” in the transition.

(...)

Sabine Nallinger, who ran for mayor for the Greens, noted that data exchange was especially problematic and didn’t work properly. Schmid agreed, telling Munich’s largest newspaper, Süddeutsche Zeitung, that “Linux is very expensive” because of the need for custom programming.

And getting rid of all proprietary software isn’t realistically an option. That 2008 EC report noted that Munich uses 300 “specialised administrative software packages” to perform its official duties. Although the goal was to replace those proprietary applications with platform-independent alternatives, the reality is that most would probably end up running in Windows inside a virtual machine, which of course requires paying Microsoft a license fee.

[Shorel]

"would probably" are in the top ten of weasel words.