That just says that we can not use them only if the ads are similar in format. It appears that we can use other ads on the same page if they would not be confused with AdSense – and if the other ad service allow it in its TOS.
Check the ToS for the other ad network as well - most of those that display ads in a similar way to AdSense will still not allow their ads to be displayed alongside those from a competing provider.
In order to prevent user confusion, publishers may not display Google ads or search boxes on websites that also contain other ads or services formatted to use the same layout and colours as the Google ads or search boxes on that site. Although you may sell ads directly on your site, it is your responsibility to ensure that these ads cannot be confused with Google ads.