This work was supported by the Netherlands' Organization for Scientific Research (NWO).
Writing Ipe next to my real work would have been impossible without the existence of some very convenient software packages. I was especially fond of GNU Emacs and its C++ mode, which found many errors I made even before I started the compiler. Ipe itself is heavily based on the PLAGEO library by Geert-Jan Giezeman, without which Ipe would never have seen the light of the world. A former version of Ipe also used the FORMS library by Mark Overmars.
As for the design and user interface of Ipe, many people here at the department proposed one or the other thing. Mark suggested the Mark object type, and it was named in his honor. Maarten suggested using LaTeX itself to figure out the size of bounding boxes for text objects, which I consider a nice and funny feature of Ipe. Many of our students participated in the development of Ipe by serving as alpha-testers.
Finally, thanks a lot for your moral support, Jules, Vincenzo, and Anil!