... That would mean, customers would pay the software,
but not  get the guarantee to make it working ... ?

I believe that is the way to scare away everybody thinking about using linux. You have to pay for a program, and then the company won't even help you get it working! Community support would be a good incentive to support a platform, and this is area is one where the Linux Audio scene fares strongly. Rarely is there a question unanswered on this list, and rarely can the problem genuinely not be fixed. IMO that is the basis for a healthy environment for development of software, weather it be closed or open sourced.

The cost involved in porting software may be negligible, but the cost involved in testing & QA for another platform is conciderable. If the linux market share doesn't make it worth its while for this company to support the linux platform, it won't do so. Having said that, I strongly encourage commercial software companies to support the platform, as I feel its the best one out there for low-lat audio :)

-Harry