How to display Adsense and Baidu Theme Promotion ads at the same time

Google and Baidu ads can coexist. For a long time, I've seen many websites simultaneously displaying Google AdSense and Baidu Theme Promotion, and even Yahoo ads. I was quite puzzled. Isn't it true that Google AdSense's program policies prohibit the concurrent placement of other content-related types of ads? Many webmasters have also asked the same question in forums like Luowozhe, and everyone speculates that sites which run both Google AdSense and Baidu Theme Promotion are larger ones, and that Google AdSense probably has more lenient policies for big clients.