The only thing you don't need a license for is for purely speculative work, generally interpreted as nothing more than idle curiosity. Even research (such as trying to build a new invention out of an old one) is technically patent infringement unless you have a license.

Here's the actual law:

     Except as otherwise provided in this title [35 USCS Sects. 1 et seq.], whoever without 
     authority makes, uses or sells any patented invention, within the United States
     during the term of the patent therefor, infringes the patent.

It says nothing about noncommercial use.

If you want confirmation, ask Duke University. It tried to argue that non-commercial research use should be protected in the case Madey v. Duke University. It lost. The Federal Circuit (the court that deals with patent appeals) held that research use is still use of the invention and still violates the law. http://www.bakerbotts.com/infocenter/publications/detail.asp...

Here's another good summary of the Duke case:

    The U.S. Court of Appeals for the Federal Circuit denied an "experimental use defense"
     in a patent infringement lawsuit against Duke University, signaling that academic
     researchers may be liable for use of patented equipment and processes even without
     use for commercial purposes. The court declared that the noncommercial character
     of the research in Madey v. Duke University was irrelevant. What matters is whether
     the research "is in keeping with the alleged infringer's legitimate business,
     regardless of commercial implications." In the case of a university, noncommercial
     research is "legitimate business," subject to the patent laws.