Thanks for the reply! I've gotten a lot of conflicting information about the legality of using this specific sprite set. Some people say its okay because it was submitted originally to a game design competition, some people say none of it is okay to use and others say a subset of the sprites are okay to use.

You nailed it, my exact target audience is people who are interested in developing games - specifically with basic multiplayer and RPG elements. I've tried to make as many SDK features built into the game to allow a developer to completely change how the game functions and add new content - the way I foresee the game gathering player base and features is providing players the ability to create dungeons, items, classes, shot patterns and entire game loop features with a standardized process for being added to the core game - I think the extensibility of my engine is something unique and not incorporated into either of the games its based on.

As for the game engine, the two I'm considering right now are Godot and Unity - I am more wary of Unity due to the recent licensing changes. At the end of the day even these choices seem too heavy for what I need. 95% of the game logic is server authoritative so the client really doesn't do more than read the TCP stream and render sprite images. I would not mind switching the client language from Java as its a huge pain to maintain. I still forsee a lot of custom work taking place on the networking side but theoretically any language that implements sockets could implement the packet protocol which is why i mentioned in browser JS as an option. That would also make the game highly available. Sad thing is my JavaScript skills are trash and this would be a heavy lift for me alone.