I have a computer at home setup with SQL and IIS. I've got the forums version 9.0x running on it so that I can test any changes I make before I put them in the REAL host server out in the etherworld. My computer is firewalled and accessible ONLY by me on my own subnet inside my house so it's not being used or accessed or seen by anyone else.
It's a test box. If I make a change to the colors or layout, I can see how it works from various browsers on my own server before releasing it to the world and breaking our nice REAL forum.
For the data, I make a backup of our real forum, then download the file, and restore it to my home "server". I end up with a situation that looks and acts EXACTLY like the REAL forum does. Too cool.
OK, if all this makes sense

here is my question:
Can I download the latest code, 9.5x or whatever it is, do the upgrade at home, make sure that my modifications I've made over the last 10 months will work with the new files, do some file compares to see what I have to do to keep my look and feel and current features and make sure all is well before I upgrade the REAL server/forum (or have our gracious host do it)
Can I download the free version to do all this?
Are the files in the "free download" the SAME as if I requested an upgrade to our full licensed public version? Or are the files themselves different?
I don't want to violate any license agreements (we all gotta eat) but I really need to make sure what I run at home privately is IDENTICAL to the real one so that my testing is accurate, comparing apples to apples, and not apples to grapes.