Thank you for your question. We have designed Tynker's Minecraft integration for the purpose of teaching kids to code. You can use this for free, and there is no need to purchase Tynker to get access to any of our tools. Our paid plans allow you to access the learning materials and structured courses.
The limits on the hosted Java server are to prevent outright playing. There are no limits on coding, but just playing on the Minecraft servers.
Unfortunately, at this time, we do not have a business model that sells the technology to build games and host your own game server on Spigot. Our primary focus is in educating kids.