Hi Sean, and welcome to the forum!
Project5 was not designed to control outboard synthesizers and it does not have any MIDI output capability (other than sending MIDI synchronization/timing to allow outboard hardware to stay synchronized with Project5). Instead, it is a soft-synth studio and live instrument with a cool sequencer and arpeggiator.
However, as you have read, RGC:Audio has created a software synthesizer whose purpose is to send its virtual MIDI input to a physical MIDI output port. This will allow Project5 to send MIDI data to an outboard hardware instrument. It does work well for this task.
You can download the MIDIOut plugin for free from Cakewalk at this URL:
http://www.cakewalk.com/Products/DXi/RGC.asp As far as using the MIDIOut plugin here is what you need to know:
1. Launch Project5 and create a new blank project.
2. Insert a new instrument track and select the "MIDIOut" DXi plugin as the instrument.
3. Select the MIDI source for the track as usual.
4. Open the MIDIOut DXi's user interface by clicking in the track on the instrument interface button.
5. In the MIDIOut DXi's user interface click once on the text "MIDIOut" to open a popup list of MIDI output ports on your system.
6. Select the MIDI output port that your hardware synthesizer is connected to.
Now play your controller--the MIDI data should flow out to the hardware synth. If you use Project5's sequencer to record your performance it will be remembered in the track. On playback of the track the MIDI data will also flow out to the hardware synth. After you're all done MIDI editing and recording you can insert an audio track and select the audio input that your hardware synth's audio output is connected to. Arm this audio track for recording and playback your sequence. It will record the audio of the hardware synth being played by the Project5 MIDI sequencer.
-Techead