http://www.oracle.com/technetwork/articles/java/raspberrypi-1704896.html would suggest that it works more or less out of the box, using the official oracle-optimized java, but with debian instead of openwrt. Now we just need someone with an almond+ to actually try ;-).
I do run it just fine on a Raspberry Pi Model B here at home, and they've mentioned that as they are working towards version 2.0, they are trying to optimize for smaller platforms. The real trick (other than running it on an Almond+) is somehow getting access to the Z-Wave and ZigBee hardware in the Almond+ to actually *do* something with OpenHAB.
As of right now, I haven't heard of a way to interface with the Z-Wave or ZigBee chips, and there doesn't appear to be any plans to give us that access (at least not at the moment, maybe further out).
Edit: Just reading my other thread again about the SDK, while there doesn't appear to be an official "API" of sorts that we can call, I wonder if the SDK can be used to build an app/function/add-on for the Almond+ that exposes a function like that?
The home automation software side of things here breaks down in to two parts then:
1) Getting the functions people want most (whether it be built in to NutsOS or alternative software)
2) Making sure there's a way to access those control functions remotely, or from another device
For example, I can run OpenHAB on my Pi while we wait for the HA side of NutsOS to take shape, but I'd love to use the Almond+ as my Z-Wave hub. For this to work, the RPi would need to be able to make calls to devices and such on the Almond+.