Here is the about us section on that site:
he main difference between us and the developer is that we do not offer any technical support for free. This is how we are able to redistribute the items at a fraction of the original price.
So, if you can think you will need ongoing technical support for a product then please consider buying from the developer. Links to each developer are provided on the product pages.
We think we make it perfectly clear that whilst the products on GPLPlus are the original products – we are not the original authors. We are simply redistributing the software, as it is our right to do so, under the GPL licence. But for the avoidance of any doubt or confusion:
We are not connected, associated or endorsed by any of the companies whose products are mentioned on this site. Any mention of these companies is purely so that our customers are not misled as to the original source of the product and so they have the choice whether to buy from us or from them.
are they legit? As I have seen most of these themes are really having 100% GPL licence.