You can run these side by side, but as of today, the 30 day trial period countdown begins.
There have been numerous fixes and changes since RC-19, we recommend using the current 0.8.00 release going forward
There will be a new purchasing flow in the near future to allow bespoke purchasing of features and updates for each license key you own. There will likely be an offering for purchasing MillMage and LightBurn at the same time in the future, but not currently.
Pricing and other FAQ’s can be found here: MillMage Licensing and Pricing FAQ