Situation
The tag wiki excerpt of the parental-controls tag makes it clear that the tag is Windows-specific.
Problem
But Mac- and Linux-using parents, too, might want to impose parental controls upon their kids.
Solution
I propose that the excerpt should be replaced with the following:
"Parental-control tools are usually used by parents to help control their kids' use of technology. Time limits, monitoring, Web filtering, social-networking monitoring, preventing the use of mature games such as Grand Theft Auto, and so on."
Bonus idea
If it's OK with you, the full tag wiki could also say: "Parental-control tools can also be used by adults, to serve as self-control tools."
Side notes
(Yes, I know web-filtering exists. But the two tags are different. Not all web filtering is imposed upon kids (some is self-imposed). And not all parental controls are about web filtering. Some parental controls are about time controls, or Facebook-friend monitoring, or other such things. So the two tags should be kept separate. You could add a "see also" if you wanted.)