The wxWidgets source code cites these copyright holders in the wxRegEx (Regular Expressions) Library.
Copyright: © 2000 Karsten Ballueder <ballueder@gmx.net>
2001 Vadim Zeitlin <vadim@wxwidgets.org>
In addition, the wxRegEx Class Reference in the wxWidgets documentation presents the following information about copyright holders on the wxRegEx Library:
It is built on top of either the system library (if it has support for POSIX regular expressions - which is the case of the most modern [Unix OS's]) or uses the built-in Henry Spencer's library. Henry Spencer would appreciate being given credit in the documentation of software which uses his library, but that is not a requirement.
On platforms where a system library is available, the default is to use the built-in library for Unicode builds, and the system library otherwise.
Notes