[Aeolun]

Ostensibly Microsofts browser team is the size of Googles’. They could just fork once and never look back.

Merging incompatible changes seems like a win compared to doing everything themselves.

[benatkin]

That's what Apple did by forking KHTML and starting the Webkit project. KHTML is still maintained and both KHTML and Webkit can be used in KDE.

[halter73]

And even more recently with Blink forking WebKit.