how can i go about making a custom NSMenu for a menulet such as this?
Is this an NSMenu or is it a borderless window and if so how would i go about this? Thanks!

how can i go about making a custom NSMenu for a menulet such as this?
Is this an NSMenu or is it a borderless window and if so how would i go about this? Thanks!

It's an app running running on the OSX status bar.
See Status Bar Programming at Apple. Also, NSStatusBar and NSStatusItem
This SO post has some additional pointers:
More specifically it could be an NSPopover, an NSWindow, or even NSStatusItem.view's custom view. In the case of an NSWindow (often a utility form of NSPanel) (or the NSPopover) you would manually open the window when the status item is clicked, using the status item's -(void)setAction and -(void)setTarget. If you use a custom view for the status item, this would be done in -mouseDown:.
Check out this post - I found it useful.
Look at the documentation for NSStatusItem. I believe you can have it display a view instead of a standard NSMenu which is what it looks like they are doing in that image.