No other non-Automattic Plugin developer would be allowed to host a Plugin in the Repository if it did anything remotely like this.

This.

Obviously Automattic have a duty to their investors to maximise their revenue streams, and making the free/donationware option hard to find is fairly standard practice, but the non-free nature of Akismet severely weakens the case for not allowing other commercial plugins (or themes, for that matter) to be hosted on wordpress.org.

Also, since Automattic consider $30 adequate compensation for losing a year's ad income on an average wordpress.com blog, asking for twice that amount to use Akismet on an average ad-hosting wordpress.org blog seems... disproportionate, shall we say?