Free OS does not prevent paid-for software
Just because the OS is free, this does not mean that a software house cannot charge for its wares that run on that OS.
The various public licenses have clauses that state that you cannot incorporate free code in charged for software, but they normally also allow you to compile against libraries from systems, and also to use the command sets in software.
So, if you have an idea which can result in a software package, it is perfectly possible to charge for that software. You don't have to contribute it back to the Open Community unless you have taken GPL or similar code and incorporated it into your package (and some of the licenses also allow a degree of that). But you can use GCC, Perl, PHP etc. to create the software including the libraries. I have wanted a HMRC certified small business payroll for Linux for ages, and would be prepared to pay the same for a Linux package as I would for a Windows package.
It is only where there is an already available good free package that you would have difficulty in selling your software. If you can sell a good DVD creation or audio editing package on Windows, you can do the same on Linux. Where is the difference? It is only people who do not understand the licensing model who think everything on Linux has to be provided free. Has the availability of Audacity on Windows stopped people selling audio editors on Windows? No,
I would agree that the proliferation of packaging tools is a problem, but you should really treat each distro as a separate OS, at least until a common packaging tool is agreed on. Until that time I will continue making the suggestion that Ubuntu is as good a candidate for the dominant distro as any.