I am not a lawyer. The Apache Software Foundation cannot 'protect Solr developers.'
Patent infringement is a claim made against someone who derived economic benefit from an invention, not someone who writes code. The patent clause in the Apache License requires people who contribute code to grant certain licenses. It does not, and cannot, prevent someone else from asserting that a user of Apache Solr is infringing on some patent owned by someone who has never contributed to the project.
