Very sensible question.
There is a spectrum of these adware companies. Some are downright criminal and will sneak the software onto your system without telling you and once it's there, hook it in real tight so it isn't going anywhere without surgery. Others are just questionable ethically; as with the EULA above you usually have agreed to install their software, even if the agreement is buried in reams of mind-numbing legal prolixity. Depending on the authors, the software may come with an uninstaller, although they're not going to draw attention to it - as they don't really want you to know the software is there. The installer may or may not actually uninstall their software - the dummy uninstaller isn't unknown.