As of version 1.3.7-beta, ProB can make use of TLC as an alternative model checker to validate B specifications.
TLC has been released as an open source project, under the MIT License. To use TLC in the ProB Tcl/Tk GUI you have to select the menu command "Download and Install TLA Tools" in the Help menu.
First you have to open a B specification in the ProB GUI. Then you can select the menu command "Model Check with TLC" in the "Verify->External Tools" menu.
TLC is a very efficient model checker for specifications written in TLA+. To validate B specification with TLC we developed the translator TLC4B which automatically translates a B specification to TLA+, invokes the model checker TLC, and translates the results back to B. Counter examples produced by TLC are double checked by ProB and replayed in the ProB animator. The translation to TLA+ and back to B is completely hidden to the user. Hence, the user needs no knowledge of TLA+ to use TLC.
There is a technical report that describes our translation from B to TLA+.