Is Seaside a Squeak Fork?

Repeatedly people mention that Seaside maintains its own fork of Squeak, what is simply not true. To see some examples read this and listen to that.

More than a year ago we started to provide the highly successful one-click images. These are pre-installed Seaside images that come bundled with VMs for the major platforms. The first releases were based on standard Squeak 3.9 images. Later versions were built using the developer images, themselves being built on top of official Squeak 3.9 images. Todays one-click images are built using Pharo Smalltalk. Into these images we installed a standard distribution of Seaside, without applying other modifications.

I don't understand why some people think that Seaside images are a fork? We wouldn't have the time and resources to do this, even if we wanted to.