It can dynamically instrument code by modifying a program after it gets loaded into memory. It was released under the Common Development and Distribution License (CDDL) in January 2005 and included in Sun's Solaris 10 for troubleshooting system problems in real time. DTrace was the first component of the OpenSolaris project to be released under the CDDL.

Apple quietly introduced a feature into its implementation that allows particular programs such as iTunes to disable tracing in DTrace and other debugging tools, Adam Leventhal, one of DTrace's original developers, told Macworld UK. Also, he adds that the alteration actually breaks other parts of DTrace in a way that doesn't seem intentional. You can read the complete story [url=http://www.macworld.co.uk/mac/news/index.cfm?RSS&NewsID=20237]here[/url].

Also, in his [url=http://blogs.sun.com/ahl/entry/mac_os_x_and_the]Sun Microsystems blogblog[/url], Adam Leventhal says Apple is explicitly preventing DTrace from examining or recording data for processes which don't permit tracing.

"This is antithetical to the notion of systemic tracing, antithetical to the goals of DTrace, and antithetical to the spirit of open source," he writes. "I'm sure this was inserted under pressure from ISVs, but that makes the pill no easier to swallow. To say that Apple has crippled DTrace on Mac OS X would be a bit alarmist, but they've certainly undermined its efficacy and, in doing do, unintentionally damaged some of its most basic functionality. To users of Mac OS X and of DTrace: Apple has done a service by porting DTrace, but let's convince them to go one step further and port it properly."

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