The most recent FISPACT-II version 4.0 (February 2018) has been released through the OECD-NEA Data Bank as:

NEA-1890
FISPACT-II, Inventory Simulation Platform for Nuclear Observables and Materials Science

http://www.oecd-nea.org/tools/abstract/detail/nea-1890/

Please note that licences obtained through the OECD-NEA have various restrictions. Licences without these restrictions may be obtained directly through the UKAEA.