but then again
An iso file is not executable code.
When you glomb together all kinds of different programs together, you're making a distrobution/compilation, the only thing you have to worry about is whether you have the right to distribute it. Which you might not have, as some otherwise free things cannot be distributed with non-free things, and when you start adding contrib, shareware and demo's, non-commercial-only you can get into problems. I prefer debian. I like totally free software, as I can do whatever I like with it. If I want to burn a copy for my friend, I can, If I want to modify it, I can, If I want to try to sell it, I can, the only restriction is that I make the source available, and I cannot change the license. To not worry that I'm breaking the law everytime I offer something for download or install software at a customer site is a good thing.
If you worry over what your business model is, how you're going to make money in a proprietary way, etc then don't use the gpl. Don't use gpl software in your work, and just do the proprietary thing, and I really won't notice or care. Lots of people in open source seem to be getting-by quite nicely so far, so don't rail against something you are in no way forced to use. You can make all the nice toolkits and widgets you want for HP-UX, Solaris, AIX, etc, and you'll fit right in to their business model, and you won't have to be hypocritical about what community you are a part of. Feel free to bog your clients systems with undocumented license-servers, dongles and other bug-aboos, setup slush-funds for lobby groups, and pass lots of bad laws. Bribe polticians so the Backstreet Boys's latest album will still be copywritten 1000 years from now, get patents on everything from hyperlinking to fucking. Make sure your install CD is boxed in a third-world country where the army regularly shoots people, and your company can pay the workers 50 cents and hour.
(Obviously this became a rant not so much against trolltech specifically, just a generalized comment, some of it might apply some clearly doesn't. I'm just getting annoyed at a world where everything you do, say or participate in is becoming ever more a comodity product. For me a lot of issues are converging, and becoming the same argument. Telecommunication and internet standards are less and less technological issues, and are a part of the basic arguments over human freedom and autonomy.)
Charging for those extra bits of functionality bring back all the problems of Closed Software: registration, licenses, enforcement, etc. Do you give out the source for the extras? You can look to the windows world, where a lot of individuals make free/shareware programs and most of them do not get much money for their products unless they do things like add timelimits, distribute only binaries, and have registration codes. It seems like a lot of bother.
Instead, if you've written a program that does the 20% of features well, then adding some features a small number of users might request, would likely be relatively easy and not take a long time (I think that's a valid GENERAL claim). If your program is actually useful to a reasonable number of people, then you could probably get a company/etc to support your developement of these extra features in exchange for a recognition of their contribution. Maybe an organization/website could be formed that would help get programmers in need of such help in contact with companies willing. As OSS gets more and more mainstream, I think lots of companies will be very interested to help out, if only to look good and help maintain good relations with the developer community.