Bug Unity 3.5.7f6 personal licenses register as pro? Is this legal to use?

I'm working on a voxel game project in Unity 3 to see how far I can get with the limitations of that version of the game engine, and I did indeed have it licensed correctly as personal.

I wound up having my friend join the project, so I had him download the unity 3 editor from the download archive. He got to the editor and mentioned it having free dark theme, and I was really confused, especially since that's only in really new versions of unity.
As it turns out, he licensed it for personal but it gave him a pro license instead. I re-licensed my installation of unity 3 with a personal license and sure enough it changed it to the pro edition.

I did a quick test, and this also happens with Unity 2.6.1f3.

I'm not complaining about this, I would actually prefer it to stay since all the pro features in this version of unity are practically free in newer versions anyway, but I'd like to know if it is legal at all to use this and/or if this is a mistake or intentional doing, since I don't want to get into potential trouble.

To reproduce, just install unity 3.5.7 from the download archive and register it.

 

I couldn't license this version of Unity
Online registration: there is no response from the server!
Manual registration: the licensing system doesn't recognize the old request file.
How are we supposed to use Unity 3.x now?

 

Yeah. Any possible torrents with cracked unity 3x are also dead.