Firstly, why would this be any worse than having a badly programmed site that eats up cycles, spare or not?
It seems that you would prefer to have the developer of the site pay for your privilege of being able to play on it than have a sandboxed application run to support it.
I am startled that you looked so hard to find information about it in the FAQs and still didn't notice the icon at the bottom. It was announced when it was introduced, heck Kestas even asked us if we minded. We said "no". You can, if it causes particular trouble to you, opt-out by asking Kestas. If it is just you not wanting to have your computer run to play diplomacy, then what are you doing playing it on your PC anyway?
Of course, if you really don't want this, feel free to donate instead (think of it as a subscription fee). I shouldn't need to give you the link because you've already read it whilst checking over the whole site for an announcement when you signed up, but, for Babak's sake:
http://phpdiplomacy.net/faq.php#faq18
But really, please don't get worked up about developers' who are trying to cover their costs when giving you a service.