It is approved by the Free Software Foundation (FSF) and described as an "open-source license" by the Open Source Initiative.
The reason behind this is to facilitate the commercial use of open-source software, without placing the contributor at risk of liability.
of the IPL note a clearer definition of responsibility for software code than that of the GPL.
Unfortunately, it has a choice of law clause which makes it incompatible with the GNU GPL.
Examples of software projects licensed under the IPL include Postfix, OpenAFS, and the now-unmaintained Jikes compiler for Java.