Bashdb 4.4 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available.
Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. This free Mac application is an intellectual property of Rocky Bernstein. The application lies within Developer Tools, more precisely Debugging Tools.
From the developer:
The Bash Debugger Project is a source-code debugger for bash that follows the gdb command syntax. The version 4.0 series is a complete rewrite of the previous series along the lines of my other POSIX shell debuggers and other debuggers mentioned below.
You may want to check out more software for Mac, such as FMMenulet, eclipse-php or Prototypes, which might be related to Bashdb.