that's correct. You basically end up serving your content to crawlers dressed up in html. it's not very hard to do but it presents quite a challenge. We already do this for blogs where we serve alternate content for rss readers which is an apple and oranges comparison, however the idea is more or less the same. The takeaway is that there is a way to serve alternate content to search engines and it involves following an ajax crawling scheme.
You can make your ajax content crawler friendly by following a specification google currently supports. I'm not particularly sure how much of this spec the other search engines support but it's a good start : https://developers.google.com/webmasters/ajax-crawling/