Read the OpenSSL license. There is nothing there that would cause incompatibility with any other Open Source license, with the notable exception FSF interpretation of GPL, which basically requires everything to be GPL or a subset of GPL.
While one could claim that any license that is not GPL-compatible is being done "on purpose", it's good to keep in mind that the whole problem with incompatibility is on the GPL side. Again, that's why there are no OpenSSL-incompatible licenses, no Mozilla-incompatible licenses and no CDDL-incompatible licenses - except for GPL.
One more thing to note is that if Sun released their code under GPL, it would make it impossible to guarantee a patent protection to their users, or to use that code in any operating system other than Linux - and Linux folks wouldnt' accept that code anyway due to NIH.