GPLv3 is a copy left license. If you legally acquire the source code (it’s public already, so anyone does), GPLv3 does not put any restrictions on you when it comes to building, selling, distributing, modifying the code.

I pointed out the name because trademark law is seperate.

And yes, GPLv3 has some requirements like attribution (mention the original developer somewhere), and you have to point out where to get the source code (already public in this case). Also, if you make any changes to the source code you must provide those changes to anyone you distribute too under the same license.

These restrictions apply to eg. UNIT3D too. Some (most) torrent trackers seem to violate the requirement to provide their changes to their users and want to keep them private. But I never asked them whether they’d provide me their source.

Otherwise GPLv3 does not pose much restrictions on it’s users, especially not on distribution.