This is not necessarily straightforward. Also, Oracle has form.

On the page cited there's no reference to licence/license. Fair enough - it's a release notes page. The only sub-page (using the menu on the left) that contains any reference to licence is the Contributors page, which isn't somewhere most users would head to.

The primary page - https://www.virtualbox.org/ - has one reference to Licence - and that's as part of the assurance that VirtualBox is "an extremely feature rich, high performance product for enterprise customers, it is also the only professional solution that is freely available as Open Source Software under the terms of the GNU General Public License".

And if you read that, assumed the best, and went on your way, you'd soon be in breach.

(Yes, you should probably visit https://www.virtualbox.org/wiki/Licensing_FAQ despite the above assurance on the front page -- at which point you'd learn about the Extension pack, the PUEL, and other usage constraints.)

This is Oracle. The Extension Pack has additional features particularly valuable in an enterprise environment, BUT there is no way to actually buy a commercial license and as per some other threads Oracle salespeople are advising enterprise customers to just use it anyway.

Oracle setting a licensing trap they can spring at their whim? Perish the thought!

It is unbelieveable that a company which employs such tactics against their users can survive. I know I avoid their products like plague, Java and DB included.

The extension pack is extremely easy to download by accident: for instance, it comes in the default Chocolately installation unless you pass a flag to disable it. With Oracle actively going around and sending threatening letters to enterprises with extensions download traffic coming from their IP blocks, it's easy to accidentally get in a bad situation.

This is separate from the guest extensions ISO image, right?

What kind of functionality do the extensions discussed here cover?

Yes, this is separate from the guest extensions. Here's information on it: https://www.virtualbox.org/manual/ch02.html#intro-installing

I would love to know thw answer to above question

I'm pretty sure the GP means: Be careful not to install unlicensed proprietary software thinking it's part of the free software that has basically the same name.

sometimes you just want a simple vb ubuntu vm. however virtualbox locks copy paste from host to vm support behind extensions which are free only for personal use(which you are using but good luck proving that in court)

No. Copy-paste is not locked behind the VirtualBox Extension Pack. It requires the Guest Additions, which are completely different from the Extension Pack.

Extension Pack gives things such as USB passthrough.

It's kinda weird that VirtualPC way back when is the only VM software I recall using that had copy-paste without guest extensions. Granted, it just typed text into the keyboard, but it was really handy none the less.

I've taken to a macro that automatically "types" the contents of the clipboard when I hit a hotkey. Super useful with VMs and remote access.

does that work fine with lag? No dropped characters?

That is indeed a problem :-) I had to bump up the delay between characters and particularly slow connections or serial consoles still can bite me. Mostly I still consider it worth using though, since fixing a few small typos is less work than typing the whole thing by hand.