Downloading MacStumbler 0.75 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. The following version: 0.7 was the most frequently downloaded one by the program users.
The actual developer of this free software for Mac is Korben. The program relates to Internet & Network Tools. 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.
From the developer:
MacStumbler is a small utility to emulate the functionality of projects like netstumbler, bsd-airtools, and kismet. It's meant purely for educational or auditing purposes, although many people enjoy using these types of programs to check out how many WiFi (wireless) networks are in their area, usually known as "war driving".
MacStumbler only works with AirPort wireless cards, it does not (yet) work with any PCMCIA or USB wireless devices.
You may want to check out more Mac applications, such as Throttled Pro, which might be similar to MacStumbler.