since docker desktop is licensed , is it possible to run spryker solely using docker engine ?

This is how it runs on Linux, yes. Without docker desktop, only docker engine. I'm not sure though it will run without docker desktop on WSL2 or on Mac.

I actually did some research for this topic a while back. WSL and docker are different things, it's true that docker desktop provides nice support for WSL2, but it's not impossible to setup WSL2 with docker without using their licensed software. Reference - https://dev.to/bowmanjd/install-docker-on-windows-wsl-without-docker-desktop-34m9