via make.wordpress.org => original post link
If your plugin is a FEATURED or BETA plugin, which means officially recognized as such by the WordPress project, you will no longer be able to add or remove committers, nor will you be able to change ownership.
This change was made due to the high profile nature of those plugins, and the potential for abuse if a plugin is given to someone who turns out to be malicious. We hope that it will prevent issues like a featured plugin being turned into a premium-upsell plugin.
This does not relate to the size of a plugin. If a 2-user plugin is made a Featured Plugin, then it will be have this limitation. That said, it also will not cause any change to proposed feature plugins or self-declared beta.