back subject to conditions of payment does not deprive the buyer of the right to enforce the patent as its owner even though it might cease to be an owner for failure to pay for the patent. That principle was established in Waterman v. Mackenzie, 138 U.S. 252, 11 S.Ct. 334, 34 L.Ed. 923 (1891), although Waterman may have involved a transaction originally designed either to keep the patent for a fountain pen out of the hands of creditors, or to ensure passage of the rights down through Waterman’s family. Furthermore, a seller’s right to take back the patent in the event of bankruptcy is not a reservation of rights so substantial as to defeat the claim of the buyer to ownership of the patent. Vaupel Textilmaschinen KG v. Meccanica Euro Italia, S.P.A., 944 F.2d 870, 874-76 (Fed.Cir.1991) (<HOLDING>). This clear law prevents Defendants from
holding that the assignor of a patent retained substantial rights in the patent and must be added as an indispensable party holding that where patent owner licensor retained substantial rights under license agreement licensee did not have an independent right to sue for infringement holding in a patent infringement case that plaintiff lacked standing where it held a conditional right to license a patent and enforce license agreements but did not have the right to transfer the patent holding that an exclusive license granting the licensor a reversionary interest in the patent in the event of the licensees bankruptcy was a grant of all substantial rights such that the licensee could sue for patent infringement holding a nonparty to a patent infringement suit who funded an unsuccessful challenge to a patent could not file a subsequent lawsuit again challenging the patent