Since its beginning, when I first announced on stackexchange.com (by subtly asking the question, whether such a plugin would be possible at all) that I'm going to give this project a try, the development of the Mathematica plugin had a lot of support. People instantly offered to help by testing and evaluating even the most crude first versions. That gave me a lot of encouragement and the feedback showed which features need attention and what others expect from an IDE.
If you like to support the plugin development, it would be very nice when you report bugs or give feedback. Of course, there is always the possibility to make a direct donation via PayPal which is a nice way of saying thank you, I appreciate your work. Currently, five people dontated money: DGK, BF, ESC, RF, FB.
We do have a great deal of official support for such a small project. I'm honestly grateful that companies actually care about open-source projects and support them by giving away very expensive things for free.
Wolfram supports the development of the plugin with free licenses to ensure that we can test and verify Mathematica behavior on all major platforms. Addtionally, to provide documentation of Mathematica functions inside IDEA, the plugin contains the extracted usage messages of many built-in functions. Usually, it is not possible to provide this in an open-source project, because this content is property of Wolfram Research. Fortunately, the makers of Mathematica where so generous to allow the publication of function documentation packed with the plugin.
The makers of IntelliJ IDEA support plugin developers in many different ways. Beside giving the community edition of IDEA as open-source software for free, they for instance allow their employers to help other developers with their API in the Jetbrains Developer Forum. The best part is that they even give away licenses for their premium products so that open-source developers are able to test their plugins on IDEA Ultimate. The Mathematica Plugin for IDEA too got a free license of IDEA Ultimate.
To evaluate performance and track issues, a profiler is a very helpful tool. YourKit, LLC is the creator of such an innovative Java Profiler (and the YourKit .NET Profiler). We like to thank the YourKit team for supporting our open-source project with its full-featured Java Profiler by providing licenses completely free of charge. The big advantage of the YourKit Profiler is that it can easily be used with IDEA during plugin development.