On the homepage (6th feature) "As Slowy mainly is a GUI for built-in OSX tools, it will occupy only few MB of your RAM and nearly 0% of your CPU."

I'm pretty sure Network Link Conditioner is the same.

I think the author would be better off giving it away for free, earning goodwill and making a name for his dev shop, then releasing other apps to all the people who now are aware of him.

Or sell it, and earn good will because he sells good products?

It's possible that within the Mac App developer community he might earn goodwill by giving it away, but I don't think it's going to make a difference for the average users.

I can't recall the names of any dev shops for the OSX products I have purchased, much less the ones I use for free.

I have no problem with people selling simple tools that make built-in features more accessible.

This also works on 10.5 and 10.6

The per-port throttling is different, the rest is quite similar ( that's what I get from reading the page ).