How can I remove apps from my purchased list?

You can't erase history, you made the purchase, it will always be a part of your purchase list. You can hide it from the list. Right click over the name of the app and choose to hide the app.

Moral of the story: be very careful what you download from the App Store. Bought a useless program and can't get rid of it. The publisher, and everyone else, will hear about it.