[keikobadthebad]

The article seems to gloss that WP is made available under GPL2+. What's the point attacking Automattic for making money when they fund the core development and make it available to everyone? It's even still available to WP Engine, the lawsuit is about trademark usage, not copyright.

From the perspective of GPL distribution rights, what exactly from Automattic 'scares [your] contributors away'?

The article says you stopped contributing because you weren't getting paid and it's demotivating to see Automattic were making money and yourself not. That's certainly understandable, but it's the same as, eg, linux kernel work. Huge numbers of devs are well-paid to contribute by companies and other devs not. You do have the option to try to get a gig being paid, as well as the option to stop or continue unpaid contribution. But it's not really valid to blame either project if some can make money from it.