com.ibm.icu.math.MathContext Java classes from the ICU4J project.
This version includes a small bug fix in the implementation of the pow() function. See this answer on Stack Overflow for more information (note that you will need 10K+ reputation on Stack Overflow in order to view the answer because the question was deleted by a moderator).
The author of the translation has stated:
BigDecimalJava classes that IBM implemented for the ICU4J project. They are licensed under the same license as the original classes, which essentially means that they may be used freely, provided that the copyright information remains.