The size difference is not much ... minibb 900kb, that "ajax" forum is an extra 400kb to 500kb - with new generation hardware and increased space available on share hosts these days both are really light weight, and cpu/resource consumption seems to be comparable in both cases.
900 Kb for miniBB? Our zip package size is less than 180 Kb, unpacked 473 Kb, but this is all because there is a big manual (150 Kb), there is README and COPYING license which are 17 Kb, and there is a lot of files which could be removed, and then the working files size is less than 250 Kb UNPACKED. Ok you can add checker tool which is about 35 Kb, and each new feature basically brings a 'weight'... but this is still less than for blursoft forum (1.2 Mb
The question is here not about the new generation hardware or specially web space: in the scripting world, each Kb has importance because this script maybe called by THOUSANDS of users at one time... and as less size it has, as more resources it will leave for other tasks, as more visitors will be allowed to enter. I doubt metaforum can handle hundreds of users per seconds, but miniBB can.
There is no issue of bringing chat software here, and what may seem to be handy for a small handful ( and hence not worthwhile implementing) may actually become useful when actually it is there ( like gmail, while others were stubborn to implement these features)
You're right, Gmail was the website giving this AJAX "technology" a breathe, but you should agree it all is a political question... In the software world, there is a lot of politics too. miniBB was always being out of politics... most probably it stands more closely to some religion... Buddhism... or similar. But we hate politics here ;-)
Maybe some one is going to create a $5 ajax list tool too
Regarding our rates it pays the 15 minutes of our job and I doubt it would be possible ;-)
For such price you can't buy even a pack of cigarettes in Europe ;-) Not saying about food... I doubt programmers should be at the stage when they work just for "thanks".