So, let's see... I followed the detailed installation instructions that blackmacros and avparker so kindly wrote. And it starts nicely and all but when choosing the Video source the mono subs2srs crashes... here is the terminal log
$ subs2srs
System.ComponentModel.Win32Exception: ApplicationName='ffmpeg', CommandLine='-i "/Users/..../Dorama/My Girl/My Girl ep01 (704x396 DivX6).avi"', CurrentDirectory=''
at System.Diagnostics.Process.Start_noshell (System.Diagnostics.ProcessStartInfo startInfo, System.Diagnostics.Process process) [0x00000] in <filename unknown>:0
at System.Diagnostics.Process.Start_common (System.Diagnostics.ProcessStartInfo startInfo, System.Diagnostics.Process process) [0x00000] in <filename unknown>:0
at System.Diagnostics.Process.Start () [0x00000] in <filename unknown>:0
at (wrapper remoting-invoke-with-check) System.Diagnostics.Process:Start ()
at subs2srs.UtilsVideo.getVideoInfoStr (System.String file) [0x00000] in <filename unknown>:0
at subs2srs.UtilsVideo.getAvailableAudioStreams (System.String file) [0x00000] in <filename unknown>:0
at subs2srs.DialogAudioRipper.textBoxMediaDir_TextChanged (System.Object sender, System.EventArgs e) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Control.OnTextChanged (System.EventArgs e) [0x00000] in <filename unknown>:0
at System.Windows.Forms.TextBoxBase.OnTextChanged (System.EventArgs e) [0x00000] in <filename unknown>:0
at System.Windows.Forms.TextBoxBase.set_Text (System.String value) [0x00000] in <filename unknown>:0
at System.Windows.Forms.TextBox.set_Text (System.String value) [0x00000] in <filename unknown>:0
at subs2srs.DialogAudioRipper.buttonMediaDir_Click (System.Object sender, System.EventArgs e) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Control.OnClick (System.EventArgs e) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Button.OnClick (System.EventArgs e) [0x00000] in <filename unknown>:0
at System.Windows.Forms.ButtonBase.OnMouseUp (System.Windows.Forms.MouseEventArgs mevent) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Button.OnMouseUp (System.Windows.Forms.MouseEventArgs mevent) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Control.WmLButtonUp (System.Windows.Forms.Message& m) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Control.WndProc (System.Windows.Forms.Message& m) [0x00000] in <filename unknown>:0
at System.Windows.Forms.ButtonBase.WndProc (System.Windows.Forms.Message& m) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Button.WndProc (System.Windows.Forms.Message& m) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Control+ControlWindowTarget.OnMessage (System.Windows.Forms.Message& m) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Control+ControlNativeWindow.WndProc (System.Windows.Forms.Message& m) [0x00000] in <filename unknown>:0
at System.Windows.Forms.NativeWindow.WndProc (IntPtr hWnd, Msg msg, IntPtr wParam, IntPtr lParam) [0x00000] in <filename unknown>:0
...mono[1944] <Error>: kCGErrorCannotComplete: CGSDeviceGetGeometry: Invalid device window
...mono[1944] <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged.
...mono[1944] <Error>: kCGErrorCannotComplete: CGSDeviceSynchronize: Invalid ....
Not sure if this is important but I placed the subs2srs folder with the executable inside the Progs folder. Also the Output folder is there. So, basically it's ffmpeg, Output and subs2srs inside the Progs folder which in turn is inside my Home folder...
I also kept X11 open the whole time...
By the way... Thank you for the great App! Well I did test it on Windows first but was too much hassle booting into it just for that...

And Preview is not really a must so...
Snow Leopard 10.6.4
subs2srs v20.0