The box my Makita plunge (rail) saw came in actually is an original-style, size 4 Systainer, and I assume it was made by Tanos. Makita have since varied the design, but the new ones still lock with original Systainers.
My understanding is that Tanos own the design rights for the original system, but Festool chose the colour scheme. My _guess_ is that the newer design used by Festool (with the green triangular locks) has some IP that they own, in case they want to use a different OEM at some point.
The new-style Systainer for the Domino XL, incidentally, is even taller, as the tool won't fit horizontally in a normal one. It is stored pointing diagonally downwards, supported on a polystyrene insert.
I have made
a couple of plywood boxes of similar size to a Systainer (for my sanders), and they are fine. I was going to make more, and may yet do so, but time and materials costs make them more expensive than the proper things. And they don't stack with them, either!
I have also had a Bosch "L-box" (or a similar silly name). That was simply ridiculous - nasty space-wasting design and fragile.
If Lidl sold Systainers occasionally, they would have long queues for sure!
E.