You don't need a commercial version, many projects get away with selling just a commercial license to the same version. As long as they have the rights to relicense this works fine.

In my company we used their stuff often. They have an optional commercial license for basically all their products. The price was very reasonable as well.

I think they might sell a commercial version as well. It makes sense with the GPL. But I can't really recall that well.

Many bare metal or RTOS systems consist of a handful of statically linked programs (one or two bootloaders and the main application), many companies would rather find a non-GPL library rather than open up the rest of the system's code. Sometimes a system contains proprietary code that may not be open sourced as well.

It matters because:

1) you may not have the right to open the rest of the code on the system 2) although you make money when you sell devices, it also makes cloning trivial

Yes it matters a lot?

He probably meant viral or tried to make a deadly twist on virality