Rondo
After a successful run of over 10 years, my MIDI playing app, Rondo, has been discontinued. If you need to re-download the app you can do so here. You can also get a free copy of the license here
Virtual Serial Port for OSX
An ongoing project to implement a Virtual Serial Port for MacOS can be found here.
UPDATE MARCH 2020: With MacOS 10.15 ‘Catalina’ the entire approach to handling serial ports and other low level software has changed completely, so it is unlikely that I will spend any time improving this.