Open Source Drawing Software

From Skencil to Inkscape, open source drawing software has been in our midst for years, with dozens of variants on the theme, and hundreds of code contributors worldwide.  One among many, Alchemy offers "an open drawing project aimed at exploring how we can sketch, draw, and create on computers in new ways. Alchemy isn’t software for creating finished artwork, but rather a sketching environment that focuses on the absolute initial stage of the creation process. Experimental in nature, Alchemy lets you brainstorm visually to explore an expanded range of ideas and possibilities in a serendipitous way."  As alternatives to Illustrator or Photoshop, most come up a few tools shy of satisfying, but as screen-based sketchbooks, they are great to have in the mix.