Rick has had numerous problems over time with scammers wrapping Paint.NET with scumbag installers and with "backspaceware" distributions. He's documented these issues in his blog:
http://blog.getpaint.net/2009/11/06/a-new-license-for-paintn...
http://blog.getpaint.net/2007/12/04/freeware-authors-beware-...
http://blog.getpaint.net/2011/10/03/paint-net-v3-5-9-and-dow...
http://blog.getpaint.net/2010/12/22/photoshop-filters-and-mo...
For as long as I've used Paint.NET (since v1) his home page and download page have never obfuscated or tried to lure users into downloading and installing crapware.
EDIT: Just turned off my adblocker and see I'm sadly very wrong about the crapware download ads. My other points still stand though.