It depends on the TOS of BOTH parties.
With Adsense you can use any "legal" network you want.
Now if that network doesn't like Adsense that's another forum but isn't an adsense question
With Adsense you can use them as long as you don't try to imitate Adsense "with isn't really possible unless you paste "Ads by Google" on the ads LMAO.
Don't let TOS unclarity scare you from other opportunities.
What it all mean is.
Google: Don't be having ad that imitate our ads or trying to use our name, and make people think we are responsible for those ads.
example: Selling #*$! enlargement in a ad that make people think it's from Google.
other then that your cool.
No network has an exclusive right over your site "unless you set up an exclusive deal", and any legal term you agreed to, the final verdict is the courts "not the TOS".
I seen ton of non competitive, no competes, exclusive policies, etc kick out because they interfere with a persons or business ability to earn a living, exclusive dealing, etc.
ask for forgiveness, not permission.
what could happen.
You get A email warning, you can't use Network X with Network X at the same time. OK remove the least profitable, case closed. AADS