Matt Mullenweg, co-founder of WordPress and CEO of Automattic announced on Reddit that WP Engine initiated legal action against WordPress, Automattic, and Mullenweg himself. Mullenweg wrote that WordPress is countersuing.
WP Engine is a leading managed WordPress host provider that Mullenweg alleges is violating the WordPress trademark.
That depends on the license.
I have to keep track of our FOSS licenses at my job, and we have to avoid certain tools that feature licenses that do actually require upstream contribs. They usually only specify this as a req for commercial use of the tool, as a way to prevent someone taking the FOSS tool, adding new functions, profiting off the free work, and giving nothing back.
The Reciprocal Public License is one example.