If patent does apply (and there's been no statement or claims about which ones do definitely apply), then people assume it's US6735595: Data structure and storage and retrieval method supporting ordinality based searching and data retrieval.
The software from HP is under the LGPLv2.1 which says "Finally, software patents pose a constant threat to the existence of any free program. We wish to make sure that a company cannot effectively restrict the users of a free program by obtaining a restrictive license from a patent holder. Therefore, we insist that any patent license obtained for a version of the library must be consistent with the full freedom of use specified in this license."
That can imply that there are no additional patent protections should you use the LGPL'ed version of Judy or its derivatives. YMMV. Consult your nearest patent attorney for details.
The software from HP is under the LGPLv2.1 which says "Finally, software patents pose a constant threat to the existence of any free program. We wish to make sure that a company cannot effectively restrict the users of a free program by obtaining a restrictive license from a patent holder. Therefore, we insist that any patent license obtained for a version of the library must be consistent with the full freedom of use specified in this license."
That can imply that there are no additional patent protections should you use the LGPL'ed version of Judy or its derivatives. YMMV. Consult your nearest patent attorney for details.
The patent expires in 7.5 years.