Download of Userscripts 4.4.5 for Mac was available from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This free software for Mac OS X was originally designed by Justin Wasack. 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. Userscripts for Mac is included in Developer Tools.
From the developer:
Userscripts is an open source Safari extension that lets you save and run arbitrary bits of JavaScript code for the websites you visit. The application implements a Javascript editor right in your browser for a simple method of creating and saving your code.
You may want to check out more software for Mac, such as Cruz, which might be similar to Userscripts.