<p>I think this mostly applies to web applications, since you often see things like language and database vendor in regards to web applications, but not so much on desktop applications.</p>

<p>If a web application is created using language X, would that have any noticeable impact on who deploys the application? For example, would a company that uses .NET products ever consider using a Python application that meets their needs or would they tend to find a .NET product that they could use?</p>

<p>EDIT 1: Refined the question to refer to apps meant to be deployed, not just used.</p>

It really depends on how much customisation and integration is required - and whether the app exposes any sort of sane API to it.
For example, you might want these types of customisation:
Custom authentication via a module; platform may well be important
Generate your own reports; database is likely to be important
Act against a web service which is part of the app; protocol (SOAP, REST, custom etc) is likely to be important, but not implementation language
In addition, there's the matter of support and maintenance - a Windows ISV is likely to be better at keeping IIS running than Apache, for instance, and the reverse. Likewise it helps if you've already got servers running the required operating system...