IInventory is the vanilla way of handling item stacks. Nothing inherently wrong with it, per say, but Capabilities is a thousand times more flexible and mod-compat-friendly.
BlockContainer is outright rubbish though. No mod will ever want to use it. It's not even great for what vanilla wants to do with it.
Unfortunately, it is not possible for me to own the trademark on "Minecraft Forge" due to it's use of the word "Minecraft" which is part of the reason I typically refer to it as just "Forge".
So I can't file a trademark issue, but I have reported the site for viruses/malicious ads. I am hoping someone will contact me, but google isn't good at that part of things.