As of this posting, I've installed GRiPnet and the two design components but have yet to actually create anything with them, so thre answers to my question(s) may be more obvious than I think as I pose them...
If I understand your licensing model correctly, using GRiPnet to game or run a previously set up game is still free and the specialty tools to design game components are still non-free. The ability to GM a previously set up game is a nice touch, giving us a 'market' (I use the term to include freeware) for ready to run adventures.
How much do we need to add to make an RPG as we used to do in GRiP3? Maps look as if they'll add for free, but I'm guessing that our old interactive character sheets and "smart tokens" (marker + entity code) still need to be made for each rules system that we wish to play. Am I correct? Has the new format introduced any licensing issues that weren't there when designing a GRiP3 adventure? I'm thinking of pulling together something fairly simple with relatively open licensing, such as FUDGE or TFT, as a test of my coding skills and to get an RPG of some sort up here.
Is anyone with more experience than I with GRiP4 available for a bit of hand-holding while I transit from GriP3? I can document as we go for those who follow. 
Good luck on the licensed games rental issue <g>. I'd anticipate it would be a licensing nightmare, myself. The short answer to [are there] "any licensing issues that weren't there when designing a GRiP3 adventure?" would appear to be "no, the licensing and copyright issues remain the same." I also spotted the ability to rent GRiP 4's building tools in your proposed licensing model. Neat! :)
The rest of my question concerned the mechanics of building and assembling assets for playing an RPG in GRiPnet. Can we have a bog simple example of the construction process, say for tic-tac-toe or checkers? Once the principles are laid out, I think I can elaborate on them for a wilderness encounter -- RPG's bog-simple parallel (I won't count walking down a corridor, since nothing particularly interesting happens doing that).
My thought is to have one or more folks experienced with the new setup provide a tutorial on how to build a game, perhaps with tips and tricks and best practices suggestions specific to GRiPnet. After running the tutorial and asking any questions, I'd then try to build a wilderness encounter, perhaps in FUDGE to keep the rules simple, and document my progress for other builders somewhat along the lines of what I've been doing in this thread over at RPTools.
velShandru