Because our dentist/programmer was a smart fellow (he'd have to be, given that he's active in two different complex fields) he foresaw that selling the software once was a nice proposition, but selling it repeatedly would be even better.
Hence the annual 'maintenance fee', of about 1,000 euros per dentist using his software. Do you know how many dentists there are in nl?
So, instead of going for venture capital this dentist-wannabe-programmer built himself a money printing press that printed more money than he and his extended family will ever be able to spend. At the end of every year the maintenance payments roll in and he's laughing all the way to the bank. This money machine has been printing since the early 90's and does not look like it will stop printing any day soon. And no VC made a single cent on any of that. He's so solidly entrenched that trying to attack his position is a losing proposition.
I like the avc blog, but it would be nice if stories like this were grounded in reality rather than fiction.