i had the same problem with that same site. i should have done something, but i had other things to do and i didn't really care that much then.
the most annoying was that i couldn't even download that because of awful lot of spam and waiting screens.
also, there was no mention of my site, so the publicity it generated won't benefit me in any way.
hardcoding a link to your website in loading screen or somewhere in the main menu should probably solve most problems.
anyway, in answer to your questions:
Do/would you allow other people to modify your release (repackage it, add links, ads maybe) and upload it to their site?
no, maybe only if they do an awesome total conversion mod and ask me first. but no installers and ads.
where/how should you state your stand on that?
i guess thats why there's EULAs. i don't think they really read it, however. if contacting them to get your link added to that page doesn't work, there's not much more to do. suing someone in another country is too hard and expensive to even consider that. you can maybe post a link to the real download in the comments and hope they don't remove it.
And the whole re-uploading the game part (given that the release stays intact) ... would you prefer all downloads to go trough your site(s) or does it not matter?
i still think that they should just link to my page and let the people download it from there. this way the people will always get the latest release. also forcing people to wait before they can start a download is atrocious.