https://www.careeronestop.org/jobsearch/findjobs/state-job-b...
as legitimate sources as they are run for public agencies that aren't claiming any copyright. I think there's no problem aggregating these with other job listings, including those that are paid.
The thing to remember is: they aren't being scraped "off the internet" but rather from somebody's site -- and if that site has a ToS which says the material is copyright, and/or has any other restrictions -- or there's a robots.txt that plainly forbids all form of scraping -- well, you know exactly what to do from there. Right?