Lenses for Four Third Cameras - Compatible?

I recently acquired an Olympus PEN E-PL1 from my other half for my birthday.

Had it for a little while, and the lense it came with suffered dust damage after we were hit with a massive dust storm while out shooting. It is currently being repaired. However, I have a mountain trip coming up in 3 weeks, so I'm frantically trying to find an alternative lense to bring with me.

Currently looking at Wide Aperture lense with possible Macro capabilities. I really adore the Zuiko 50mm Macro f2.0. However, I realize it's not compatible with my Micro body kit. I would need an adaptor.

My question is:

Are all Four Third lenses compatible with the correct adaptor? Or are they all set up slightly different for their Auto-Focus requirements?

Meaning: Can I widen my search for possible lenses to use with this? As it is, there's only one I really like from the Zuiko (Olympus) line. It would help if I could look at other Four Third brands, such as Nikon.

So my question is:

I have a Micro camera and I'm looking for a Four Thirds lense. I realize I need an Adaptor to do this if the lense is not a Micro lense.Am I limited to just one brand, or are all camera lenses and bodies compatible with the right adaptor?

I own an Olympus and want to explore Nikon lenses. But, I have no idea if that even works, haha.

Okay, so lets get the major issue out of the way first. Your camera will accept all MICRO 4/3's lenses irrespective of brand, it will not accept 4/3's lenses with out an adapter. Using a 4/3's lens with an adapter will provide full functionality. If you use another type of lens with a (lens mount specific) different adapter you may lose functionality.

Go to olympus website and look it up about adapters and lens compatibility. You can also use OM lenses but with the use of adapters. Try other third party lens manufacturers like sigma, tamron, tokina, ziess, etc.

Yes, all four-third lenses are compatible. No adaptor needed. The four-thirds.org web site has a list of all the lenses that are compatible.
http://four-thirds.org/en/fourthirds/lense.html