Thanks for the responses but I think I should clarify things a bit. The engineering software is low volume and high cost. It is largely written and runs on Linux, Windows and with minor tweaks would run on OSX. An older version used to run on OSX 10.3. In order to properly test and support the software it is necessary to be able to run on all the versions of the operating system clients would encounter, say, all the major versions in the last 5-10 years in all the supported languages. Typically this would be done using virtualization and typically the companies selling operating systems would provide mechanisms for software to be supported on earlier versions of their products.
OSX is not a widely used platform for engineering. I used it (along with Windows and Linux) for about 5 years and during this time it became clear that Apple was a bit odd when it came to technical support. For example, when looking to purchase a computational cluster they denied having any internal technical support and directed me to an independent consultancy for benchmarking. I tried to post this question on the developers forum, perhaps I misunderstood, but they seemed to want $99 to allow their users to answer questions for them. I have also tried to ask at one of their shops without success.
Concerning the license and virtualization, which is supposed to have improved recently!, for OSX 10.8 bought from the App store:
“(iii) to install, use and run up to two (2) additional copies or instances of the Apple Software
within virtual operating system environments on each Mac Computer you own or control that is
already running the Apple Software, for purposes of: (a) software development; (b) testing
during software development; (c) using OS X Server; or (d) personal, non-commercial use.”
So how do companies go about supporting their software on OSX? Do they purchase licenses from Apple and not the App store? If so, what is the programme called?