(Caveat - I haven't looked much at the library or webpages, simply
because it is not the kind of tool that is useful for me. Most of my
user interfaces are blinking LED's and push-buttons, rather than guis on
a PC. But I can see it being useful to many others, and maybe it will
be useful to me too in the future.)
Establishing a user base is certainly key. One thing is that it can
build up a reputation and spread recommendations amongst forums. The
other is that it is vital for feedback and making sure the project is
actually suitable for a wider base. At the moment, reports I have seen
here are all positive about the code and the appearance of the library
and tools so far. But if it is going to be be useful for many people,
then it's important to get many people to test it - otherwise you risk
ending up with a library that is perfect in the eyes of the author while
being awkward or limited in the eyes of others.
Another important point is to establish a team. Correct me if I'm
wrong, but this project is Mr. Flibble's alone, with a little outside
help in making some icons. That is not sustainable in the long term.
If people are going to use this system for anything serious, they need
to know that there is a team behind it. They need to know they still
get support and fixes while Mr. Flibble is on holiday, and that the
project will continue if he decides to move to the Andes to become a
llama farmer instead of a programmer. And the project needs people
involved in documentation, graphics design, marketing, etc. (Mr.
Flibble may also be good at these - though the skill sets are usually
somewhat separate - but there are limited hours in the day for any one
person.)
All these things are difficult to build up - and they are difficult in a
different way than designing the code and library.
Building up a base of "amateurs" - small users, students, etc., is one
possible route. But unless he also gets some "power users" who will
help out (without pay) in support forums or groups, there is a risk that
supporting and helping these users will take up too much time and leave
him unable to work on the project itself.
My recommendation (easy to say, hard to do!) would therefore be towards
getting a single good commercial corporate user interested in the
library. That would give immediately useful professional feedback on
what other users need from the tools, and a commercial contract. For a
customer company with a bit of size, this could easily have huge
potential savings compared to them buying commercial QT licenses for a
developer group - enough that it is worth the risk for them, even with a
contract size that is a large amount for Mr. Flibble's company. With
that contract in place, he can get other financial investors, hire some
people, and make a serious go of it as a commercial open source product.
However he does it, I too wish him luck with the project - it has a lot
of potential, and I think Mr. Flibble has enough practicality and
realism to make it work.