We know OpenDJ is 100% Java. Thus technically, it can run anywhere.
Below is the reply from Ludovic, the Product Manager for OpenDJ:
The truth is that historically OpenDJ (and it's legacy OpenDS) was primarily developed on Unix by Unix engineers (mostly Solaris). Remember it all started at Sun Microsystems. Since we've created ForgeRock, I've seen a big shift of use of OpenDJ, from being mostly deployed on Solaris to now being mostly deployed on Linux and even more frequently on Linux in a VMWare environment. This said, we do have customers that have deployed and are running OpenDJ on Windows servers. Coming soon, we will have a better integration on Linux with RPM and Debian packages. We already have SVR4 package for Solaris and family. We do not have plans nor requirements for Microsoft packaging, for now.
Yes, Linux (especially RHEL) on VMWare environment is what I get these days in customers' sites.
Not convinced with OpenDJ or have not play around with OpenDJ before? Download here. You'll love it!