My guess is that is an step to discontinue the product. Defold has never been a big project inside the company. Candy Crush uses Fiction Factory, and the last time I heard about internal development, Unity was a growing technology. (If you live in Stockholm you can find a job as Unity architect at King).

So, instead of silently killing Defold a second life as an open source project seems more merciful for the people that internally believed in the project.