What does "Legal status Expired - Lifetime" on a patent Design patent mean?

It means that the patent term has expired, and that the design is in the public domain.

A U.S. patent (design or utility) whose terms has run and is expired, as in your example of U.S. design patent D443661, means that the U.S. patent cannot be infringed; however, that legal consequence does not necessarily mean you are safe to commercialize the product shown in the expired D443661 patent. Before you commercialize you should commission a freedom to operate search and opinion from your patent attorney to gauge your liability exposure, if any, if you were to commercialize this product. For example, there still could be other enforceable and relevant U.S. patents, trade dress, or sometimes copyrights (e.g., if the product is non-functional). Or the search results might suggest you are likely safe to commercialize. The point is, the due diligence should be done.

Whereas with U.S. utility patents you often seem them become abandoned prior to the running of their term for lack of a required maintenance fee payment. An abandoned U.S. utility patent, like an expired U.S. patent cannot be infringed; however, with an abandoned U.S. utility patent sometimes there is a possibility that the abandoned U.S. utility patent could be "revived" so you should be a bit more careful when considering commercializing an invention disclosed in an abandoned U.S. utility patent. Note, U.S. design patents do not have maintenance fees.

Design patents issued from design patent applications filed before May 13, 2015 have a term of 14 years from the issue date.

Design patents issued from design patent applications filed on or after May 13, 2015 have a term of 15 years from the issue date.

It appears the design patent you are referring to was based on an application filed on January 10, 2001, and issued on June 12, 2001, and this design patent expired in 2015 (14 years later).

Legal Disclaimer- the information provided herein is not legal advice. Transmission of this information is not intended to create, and receipt by you does not constitute, an attorney / client relationship. Although effort has been made to ensure that the answers are correct, Law Office of Walter Tencza Jr. cannot and does not offer any warranty, express or implied that the answers contained are accurate statements of law. This document is provided for informational purposes only. Viewers must not act upon any information without first seeking advice from a qualified attorney outside the context of this document.

It is no longer legally enforceable (legal status expired) as it has run its lifetime.

Design patents have a term of 14 years. The term has expired.

My comments have been made without discussion. An attorney client relationship has not been established. There may be conflicts which prohibit my providing you with specific legal guidance. Any contact with you beyond these few general words will start with a disclosure of opposing parties so that a conflict check can be made. You should discuss with an attorney.