When the "Software MegaCorp Sues Over Some Patent" scenario was tossed about, it was usually Microsoft cast as the villain, with the usual "Watch out for Google!" voice or two. Yet, after Oracle acquired Sun, it wasn't really a surprise to learn they were choosing to be less "open" and more "profit oriented".

JRuby is a Java implementation of the Ruby interpreter, being developed by the JRuby team.
JRuby is free software released under a three-way CPL/GPL/LGPL license.
JRuby is tightly integrated with Java to allow the embedding of the interpreter into any Java application with full two-way access between the Java and the Ruby code (compare Jython for the Python language).

If languages are defined by standards, what makes them open source? Well, the specification itself can be proprietary. You'll find in older main frame languages if you wanted the specifications you had to pay huge amounts of money for the detailed specifications.

The second opportunity is the implementation itself. For example with Ruby, there are several implementations, all of them happen to be open source.