Legitimate but flawed
It's an example of the controlled distribution world meeting the internet.
The ACSE make their money from having people subscribe to their journal. A researcher submits their manuscript, without having to pay a fee, and then the society have it peer reviewed, typeset and published (all of which cost them money). It's a valid model and has worked ok for some time, but has a few flaws.
One issue is that if your paper isn't in the journals area of interest it'll be rejected. This means that areas of research go in and out of fashion, so if you're doing good quality science outside those areas, then you can't get your paper published.
Another is that if your paper is a negative result, it'll be rejected. This means that other people are doomed then to keep repeating that bit of research, which is a waste of effort, as they don't know that someone else has looked in to the same idea.
A better model seem to be the Open Access one, such as PLOS ONE, where you pay to submit papers, and then the access to them is free. The fee isn't vast, and is generally factored in to the grant money that you get to do the research. The funding body in turn saves the money from not having to subscribe to yet another journal.