>CentOS and MariaDB come to mind as two possible examples, that started as a means not to pay for the original projects
Well neither CentOS or MariaDB came to be because of 'asking for donations'. CentOS was forked from RHEL to be a subscription-free enterprise alternative and IS actually being funded by donations, which they ask for.
MariaDB is a fork created by the same person who created and then sold MySQL to Sun for $1 billion (which he was able to do due to MySQL having copyright attribution from all contributors).
I think these were at best very poor examples to support your statement.
>While it is very convenient for the users, it does not guarantee that you as the author will get paid to work on it.
True, it will be a competitive situation, however it's not very different from proprietary commercial development as you will need to continue to add features and improve performance etc, else users will turn to another application which does.
In open source it's extremely easy to fork (ie base upon existing code) however due to copyleft it won't be a fork with exclusive lock-in features as anything can be ported back, so in essence the payment will go to the person/persons who the end users think is providing the best value for their payment, again not unlike proprietary commercial development.
And in the tradition of open source software, I see no direct reason as for why developers can't consider sharing development and thus also the donations.
>The Android market is a prime example of this, where lots of apps are just plain forks, with the original authors getting nothing in return.
Well I think that is primarily a problem of original developers not creating Android versions of their open source applications to begin with, as such we are seeing opportunistic third-party developers creating quick ports of their software.
But is that really a bad thing? If the original programmers aren't interested in supporting the Android platform and someone else provides the service then I fail to see the harm (assuming of course that the licence is abided).
And I do think that when official projects enter the market place they will quickly gain the upper hand over third-party ports as not only are they again the 'official' version, but also I trust that they as core developers can typically adapt the original code better for Android use.
I also think we are slowly seeing more official Android ports of well known open source desktop software, VLC comes to mind.
Looking past whats already been discussed I'm sure there are viable venues which haven't yet been thought of, or at least given a fair chance.
One thing I forgot to highlight was the Valve Steam Workshop donation program which just recently resulted in enough money for two 6 month development contracts for working on Blender.
Again things like this makes me believe that exposure and ease of payment is the big hurdle, not that there's not enough people willing to donate for open software development.