Supporting Free and Open Source Software
Recently I became involved in Ubuntu Friendly and one of the tools I wanted was a wireframe application so I could make quick mockups moving forward. I learned about several options:
I eliminated Balsamiq because it requires Adobe Air (which is no longer being developed for Linux).
I found working with Pencil very easy to create the mockup of Ubuntu Friendly. Pencil included resources for Windows, Android, iOS and Web Applications. The drawing produced is very clear and does not simulate being drawn by hand. I had one rather important issue with Pencil; it would not export the mockup as a .png. The dialog box would come up and you would take the steps to save a file, but no file was actually saved. When making a .pdf file the table resource was not rendered.
Working with Wireframe Sketcher was not quite as easy as Pencil, nor were there as many built-in resources. The program had no tool to create a table. The resulting sketches simulate being drawn by hand and the program was able to export .png files. This software is also not free and will cost roughly $100.
In the end Wireframe Sketcher is the winner as it is able to create functional mockups without requiring Adobe Air or Java and was able to successfully save .png versions. An added feature, that I will not make use of, is that it works with Ecplipse IDE as well. If you are comfortable with Eclipse, or even Visual Studio, the application will be comfortable immediately.
The IDE style allows you to build an application with multiple screens and even have the screens be interactive. All the other mockup programs I tried lacked this depth. The program even allows for custom made svg images to be used as additional shapes or icons.
If you are an Ubuntu User like I am you can find it in the Ubuntu Software Center.