CodeBlackboard 3.0 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The software relates to Productivity Tools. According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The actual developer of this free Mac application is Numathic Inc.
From the developer:
Code Blackboard is an application designed to help you create code blackboards for reading, annotating, and sharing. It supports creating code blackboards from files, clipboards, Xcode, or command-line. You can take your code wherever you go, read whenever you want, and keep your thoughts along the way.
You may want to check out more software for Mac, such as pdf-DocPro, Instant PDF or Simply Notes, which might be similar to CodeBlackboard.