This is true (the ISL client disables the SPLM client). However, the ISL client is backwards compatible with software built with SPLM. You should be able to run any earlier version of CAESAR II, all the way back to v.5.31 in 2011. (We've tested this here.)

If this is not the case for you, please open an SR on Smart Support so that the Tech Support group can investigate this in detail.

CAESAR II v.12 will be built with the ISL libraries and this version will be available before the end of May 2020.