I doubt I’d be able to do this on the GitHub site since astah Pro would need to be installed there, but even running the hook locally and pushing the result for inclusion in the Pull Request would be a huge step in the right direction. I plan to experiment with the command line interface so that I can create a Git hook that allows designs to be exported as SVG and incorporated into our public wiki pages on GitHub. It would help my workflow to be able to do the same operations on both platforms. I’m planning to spend my own money to try astah Professional on the desktop and I’d like to see some features added to the iPad (since I have my iPad in front of me as often - or more often - than I have my laptop).
There are still things I wish it could do (their web site says it can do Notes and Note Actors, but I don’t see how, for example) but even as an evaluation tool, it has been valuable for me. UMLet runs stand-alone or as Eclipse plug-in on Windows, OS X and Linux. It was a little difficult to get used to a few things in the beginning, but I’ve become pretty proficient with it now. UMLet is a free, open-source UML tool with a simple user interface: draw UML diagrams fast, build sequence and activity diagrams from plain text, export diagrams to eps, pdf, jpg, svg, and clipboard, share diagrams using Eclipse, and create new, custom UML elements. This is a great app! I’m a lead developer for an open source Java project and I’ve been using the free iPad app for about a month.