1) I don't understand the advantage of the non-copyrighted version for $30.  Is it simply the removal of a smf likes pro logo?  If not, what advantage is the non-copyrighted advantage?

2) I run a completely different test forum & would obviously like to have this installed on the test forum, first to make sure it's compatible and second to test the features.
would i need two licenses to install it on both forums? or could i simply run the lite version on the non-live test site?

3) I tried to install the lite version on my test site but got the following error; The package you are trying to download or install is either corrupt or not compatible with this version of SMF. 

can i assume this is due to the fact that I'm running 2.0.4 on my test forum?

thanks in advance.
I think this is exactly a mod that i'm looking for.

1) I'm not exactly sure where the copyright is added (since i bought the CR version), but it's just a small text link around where this is at the bottom of the forum, below, as an example.  No difference in the functionality of the MOD if you go with or without copyright removal.

SMF 2.0.4 | SMF © 2013, Simple Machines | Blux Theme by SMFPacks.com © 2011-2013

2) Yes, we all do this. The MOD needs an extra license for 2 public forums, but A test forum of course is allowed for testing and adding your own customizing.

3) That is because the Lite MOD has not been updated to "install" for 2.0.4, but if you "version emulate" it will install just fine. PRO version updates takes priority of Lite versions, obviously, and are almost updated within a day or 2 of upgraded SMF version.

Plus purchasing the PRO version gives you much better support, on this site, which a section is unlocked once purchased.

That's just my take on your questions, you may need to wait for NIBOGO for official answers from him, but pretty sure I covered it.

1. The copyright is shown at the bottom.

2&3. hcfwesker replied them perfectly.

Thanks hfc!