> Can I control my MIDI sequencer or instrument with the Lemur?
Yes you can ! The JazzEditor software works as an OSC to MIDI bridge. (Remains in Version 1.5)
Yes you can ! The JazzDaemon software works as two-way OSC to MIDI bridge. (New in Version 1.6)

> What kind of MIDI messages can the Lemur handle?
All types of standard MIDI messages: Note-on, CC, Program Change, Pitch Bend, Sysex, MIDIClock, etc.

> I have read somewhere that is it necessary to launch a Max patch between JazzEditor and my MIDI application, is that right?
No, it is not necessary to use this stratagem anymore to use MIDI.

> You said that Mac/Win versions of JazzEditor are strictly similar. So why do Windows XP users have to use a MIDI port emulator like LoopBe to receive MIDI data from the Lemur into their application?
Under MacOSX, MIDI application are fully considered as peripherals, like a master keyboard or an external MIDI interface. Software have input and output ports which enable communication between applications. WinXP does not work this way. In order to have two MIDI applications communicate with each other internally, you will need a piece of software that emulates a virtual MIDI interface.