Why would it be illegal to inform about “abort”?

I would immediately assume it's a joke, yes.

My interpretation would be that it's some kind of reference to "abortion", i.e. stopping a pregnancy.

It is a reference to abortion gag laws, which forbid even mentioning abortion.

The Global Gag Rule was in place in the US in 1995-2009, was reinstated in 2017 and revoked again in 2021:

The “Global Gag Rule,” otherwise known as the Mexico City Policy, requires that any overseas organization receiving U.S. aid not have anything to do with abortion. Doctors, midwives, and nurses could not even mention the word abortion—much less provide abortion services with their own funds—even if it was legal in their country, or if a woman asks.

This is not directly related to software, but FSF has always been strongly opposed to all kinds of censorship legislation.