"Let's start with Java. With Java you have two options
for licensing. First, you can use (possibly with your own
modifications) the code from OpenJDK. Second, you can make a new
implementation of Java, based on the Java specification.
"There is no explicit patent license covering OpenJDK. OpenJDK
is covered by GPLv2 and it is generally believed that when one
licenses code under GPLv2 that license includes an implicit patent
license. In 2004 Dan Ravicher, senior counsel for the Free Software
Foundation, warned about the weak patent guarantees for BSD and GPL
and recommended attaching patent grants.
"This means the scope of the implicit patent license is unclear.
On the one hand if all you do is use OpenJDK unmodified you should
be completely covered. On the other hand if you made such extensive
changes that it is no longer recognizable as Java and now infringes
some Oracle non-Java patent, you would probably not be covered by
the implicit license. Where exactly you cross the line from covered
to uncovered is very fuzzy and unclear."