I would like to confirm if I can do this before I begin. I would like to use Concrete5 as my new CMS but currently still learning the development side, mainly the navigation menu which is the hardest to grasp.
The problem is that the client is on a tight schedule and would like the project sooner than later. Can I download cloneamental and recode majority of the files - colors, blocks, columns, etc. without getting into any trouble by reselling it? Probably sound like a weird question but better safe than sorry.
So in that case it's really no different to use Cloneamental versus the built in Elemental theme to build a site, you're free to do that, including hacking away at it to suit a purpose.
In the case that you're making it clear that they are purchasing actual software, it's a case of recognising that concrete5, which include the Elemental theme is under an MIT licence, and therefore Clonemental has that licence as well.
MIT licences are very permissive in that you can actually sell MIT licensed software to others, even if you didn't write it yourself, the main requirement is just that you continue to include the MIT licence. If you are following these rules, you're fine.
It really then comes down to more of an ethical question to be honest. If you are just taking something that is under an MIT licence and free, and selling it to someone as is without adding extra value, that's legal but really not that honest. Whereas if you take something MIT and then add lots of stuff, hack away at it, make it have a new value because of your input and then you decide to sell it it's a bit different - customers are then paying for the extra value (and arguably moreso your services rather than a product), and your pricing would probably reflect the value of your work you've added rather than entire codebase.