No, it's not against Google AdSense rules.
If the guest posts are scraped or contain banned content, they violate Google AdSense rules.
But generally speaking, guest post content doesn't run afoul of Google AdSense.
If you're thinking of setting up a site full of guest posts, I suggest that you have an editorial policy to maximize the quality of the content on your site.
By doing this, you abide by all of AdSense's rules and provide a better overall experience to your users.
This can produce a win-win situation for everyone involved.