Eh, you could always completly open source the code and release it everywhere on the internet. Then let the Streisand effect take care of any lawyers (and of course make it difficult to find the developer). (You can tell I don't like the current state of patents and copyright huh =P).

But it really depends on what you mean by Zune HD functionality. You mean file syncing? Then that shouldn't be to problematic. Heck people routinely do things like that for iTunes. Though I believe Apple also offers an API to do a sync with less features though (for example, Blackberry has their own app that syncs with iTunes).