> You obviously have no clue how GPL works.

I disagree.

> Everything is explained very well on the agreement page.

Yes, it's very clear that they're attempting to subvert the GPL by coercing customers into not exercising their freedom to redistribute (section 3, first sentence). I can't find it now (all I could find is https://news.ycombinator.com/item?id=11808914) but there was a thread about this issue earlier this year.

Essentially, in some people's view grsecurity is acting in bad faith which means that they are violating the GPL (not the license text itself, but the copyright law surrounding license agreements).