When leftists say that something like public healthcare would be literally free what they mean is that the net cost compared to the alternative is null or negative, not literally that nothing is being spent.
If you want to give me a link of someone who literally thinks that free college means that no one has to pay anything for the college itself or it's staff, I'm willing to take a look. Otherwise, it's just an argument that the net cost to society is negligible or negative, which is a valid use of the word too.