The following are the current version of the grading functions used for grading the quality of the antiderivative with reference to the optimal antiderivative included in the test suite.
There is a version for Maple and another one for Mathematica/Rubi. The following are links to the source code.
The following are the listings of source code of the grading functions.
Mathematica and Rubi grading function
Maple grading function