About eight years before I made a web shop with OpenCart what is Daniel Kerr project. It knew some great things what others didn't. Of course there were bugs too, what I had to fix. But I liked it, and a summer later I made my own first CMS. That was the MVC 1.0. I made it to myself, and it's still working. Then came out the Opencart 2.0. I watched it a while on github, how become to the final release. Of course it was full of bugs again, but I could see that it will be good. Although I know that is a free program, I asked permission from Daniel, to build a public version. They said yes, so I built this system.
I removed the e-commerce things, what are huge part the Opencart. I kept the core, and start a fresh project. With Opencart logic I built a software whereby anybody can make a website easy. Of course as far as possible I tried to keep major compatibility with Opencart, because it have many modules what GrandCMS can use.
So if you are familiar in Opencart, then you can develop in GrandCMS easy.