I respectfully disagree with this tweet. Creating a design for a service (Svbtle) and limiting who can use that service doesn't provide justification for essentially copying the design. You want to make a similar service, but more accessible? Fine, but at least create your own design.
Consider this: what if Samsung put Apple logos on their phones? This would be seen by most as a transgression of some sort. The point being, Svbtle's design is part of the branding for the service. Ripping off that brand, for lack of a better term, seems to me as being unjustified and wrong.
I seek to start a discussion, not a heated argument. I would like to hear your thoughts about this.