The author was modest enough to omit the name of the plugin cited as an example of poor licensing terms, but I'm not, Gravity Forms is a very popular plugin with excellent support, and it's GPL licensed.

A side note, I've often times been shocked at how little the typical WordPress professional knows about the GPL. Usually when I post in Facebook groups or in comments sections that it's legal and praiseworthy to share whichever premium theme or plugin under discussion, I'm met with gaping mouths.