What are the differences between the regular, stand-alone TOUGH2 code and the TOUGH2 forward simulator used in iTOUGH2?

The forward simulator implemented in iTOUGH2 is based on the version of TOUGH2 described in Pruess et al. (1991). However, there are quite a few updates and additions; most are described in Appendix A of the report iTOUGH2 Command Reference, in separate reports (e.g., iTOUGH2-GSLIB), or in presentations given at the TOUGH Symposia (e.g., Finsterle, 2012). The list of available EOS modules implemented in iTOUGH2 can be found on the iTOUGH2 licensing web page.