Starting with version 2019, the Wolfram Language Plugin will be part of the upcoming JetBrains Marketplace which gives developers the opportunity to make some revenue off their plugins. Not all details are clear until the official launch of the JetBrains Marketplace, but the plan is to support a license scheme that is similar to IntelliJ IDEA. That means, the following license options will most likely be available:
Free license for open-source developers
People working on open-source Wolfram Language projects will have the opportunity to get the Wolfram Language Plugin free of charge. There might be some requirements like mentioning the Wolfram Language Plugin in the README of your your project or keeping a line in each file header which mentions the plugin. This license is for people who give something back to the Wolfram community by using their expertise to provide Wolfram packages and share them with the public.
Free license for students or educators working in academia
Educators, students or people working in academia can get the Wolfram Language Plugin free of charge. The reason for that is that scientists might not always be able to share their latest research work. However, like educators, they work for the greater good pushing the boundaries of science or spreading knowledge. Therefore, people who can prove their association with a university or school will get the Wolfram Language Plugin for free.
The free license and other discounts include many more groups and for more information, you can visit the special offers of IntelliJ IDEA.
Personal license for non-commercial use
People working on private, non-commercial projects or people who want to actively support the development of the Wolfram Language Plugin can get a license for a small subscription fee which can be paid monthly or yearly.
The plan is to offer this license for approx 3 Euro/month if paid monthly or 30 Euro/year if paid yearly. The price is similar to or smaller than what you would pay for one beer in a bar in Germany.
People using the Wolfram Language Plugin for their work can get a commercial license subscription paid monthly or yearly. The plan is to offer this license for approx 12 Euro/month if paid monthly or 120 Euro/year if paid yearly.