Jape is a configurable, graphical proof assistant, originally developed by Richard Bornat at Queen Mary, University of London and Bernard Sufrin the University of Oxford. It allows user to define a logic, decide how to view proofs, and much more. It works with variants of the sequent calculus and natural deduction.
It is claimed that Jape is the most popular program for "computer-assisted logic teaching" that involves exercises in developing proofs in mathematical logic.
The program is available for the Mac, Unix, and Windows operating systems. It is written in the Java programming language and released under the GNU GPL.
References
Jape (software) Wikipedia(Text) CC BY-SA