AdSense Manager lets you manage your ads from within WordPress. With support for AdSense, AdBrite and many more.
It was a way to support development of this plugin while it was actively being worked on. It is no longer included.
If you are able please consider making a PayPal donation.
No, and Yes. While the original purpose of being able to modify colours etc. without digging into code is now gone (although still supported) there are other advantages to AdSense Manager. For example: positioning. Additionally there are some plans afoot to provide intelligent ad placing methods to make all this work even better.
There is a (nice tutorial here)[http://www.tamba2.org.uk/wordpress/adsense/] which explains positioning using code in template files. You can use this together with AdSense Manager: just place the ad code tags where it says "place code here".
To revert to an old copy of your Ad database, go to your Dashboard and add ?adsensem-revert-db=X to your URL. Replace X with the major version that you want to revert to.
If the latest version to work was 2.1, enter: ?adsensem-revert-db=2
Load the page and AdSense Manager will revert to that version of the database and re-attempt the upgrade.