Instantiations is making their software available free-of-charge for individuals developing open source software. According to the website, the software can only be used on open source projects; other uses would require that a license be purchased.
Instantiations has been part of the Eclipse eco-system from the beginning. I’ve been using their WindowBuilder product for years. In fact—if I remember correctly—I’ve been using it since 1991 (maybe 1992). Of course that was the first Smalltalk version (they still do Smalltalk). It’s a great product built on an incredible legacy and a wonderful showcase of the power of the Eclipse platform. They have several other products, including RCP Developer, GWT Designer, CodePro, EclipsePro and WindowTester.
Go here if you need to use any of these great products on your open source project.