Hi kjohann

You can try the Vivace Edition with a DEMO License for free, but just not in production.
The Moderato Edition and the Allegro/Presto/Vivace Edition are actually two differente distributions, so, if you have a Moderato Edition, you have to download the Allegro/Presto/Vivace Edition from Download.
The Try version of the Vivace Edition is already configured with the DEMO License, so you are ready to go.
The EVALUATION License instead is normally shipped to Companies which are evaluating the product in order to buy it, and I actually don't know if there are any costs. If you need the EVALUATION License, you have to contact info@lightstreamer.com and they will give you all the details.

hth
Marco