Seems Oracle bought Sun to become a java patent troll. Trying to destroy the alternative free java implementation that is part of android. Sun used to be agnostic towards Free Software in the past, then became a huge fan on java liberation day. Now that Oracle is in control and starts its quest to destroy the free java world, we are back to the dark ages. So, now what?

Oracle is still distributing a free version of java itself through OpenJDK on which IcedTea is based. Implementations derived from that source base seem safe against copyright and patent claims as long as one follows the obligations of the GPL. That is of course only for patent and copyrights Oracle holds or can pass on (through its stewardship of the JCP). To protect against claims by unrelated companies or when you have a free implementation of java not based on code distributed by Oracle, like GNU Classpath, try to get your implementation covered by a Free Software friendly patent pool. For example gcj/libgcj/GNU Classpath (as are some parts of the apache and eclipse java stacks) are part of the “System Components” of OIN (and Oracle has joined OIN).

Finally if you contribute to any Sun/Oracle java implementation demand that they change their Contributor Agreement to be truly reciprocal, not just for copyrights, but also for any patent claims covering the project you contribute to. So that anybody that wants to share the project you contributed to will always and irrevocably get all the rights to do that (not just for the GPL version). Point 3 in the current Sun/Oracle Contributor Agreement isn’t reciprocal, you grant a perpetual, irrevocable, non-exclusive, worldwide, no-charge, royalty-free license to any patent claims you might have to Sun/Oracle, but they are not granting back to you or the wider community any they hold on the project as a whole.

Source: Mark J. Wielaard