According to the About JUCE page the license is GPL, so you need a commercial license if you want to use it in a non-GPL project. The pricing doesn't look too

According to the About JUCE page the license is GPL, so you need a commercial license if you want to use it in a non-GPL project. The pricing doesn't look too bad if the library is solid (£399 for a single project, £699 for unlimited). They really need a lighter color for the text on their website -- tough to read.