I heard that a “Splitter” can be used to record HD contents such as TV programs or movies; can I use a splitter with this product to do that?

Legally, unless you have been duly licensed, we expressly advise that you DO NOT record copyrighted contents, particularly those with copy protection such as HDCP, to avoid breaking the law.
If you have been duly granted a license to record copyrighted contents, it is technically possible to use a splitter with our product; however, our warranty does not cover such usage, and AVerMedia will not be liable to any damage caused by such actions.