@ysss: I think is okay if it is removable if you have the knowledge. But if the platform is popular and there is a lot of end users that don't have that knowledge, ability and concern, then there would still be a lot of exposure for the add.
for instance: there are a lot of free templates for websites, but they have the companies emblem on them at the bottom for their exposer. You can remove it if you have the knowledge to change the script, but since it is small and a lot of people don't have the knowledge to change it(total guess, maybe 80 percent), they just let it stay and the company gets what they want. I take the time to remove it and I get what I want. Both are happy.
I'm just saying there are a lot of free things out there where the advertising that actually pays for it.