the primary platforms for svr4 were intel x86 and sparc; the sparc version, called solaris 2 (or, internally, sunos 5.x), was developed by sun. the relationship between sun and at&t was terminated after the release of svr4, meaning that later versions of solaris did not inherit features of later svr4.x releases. sun would in 2005 release most of the source code for solaris 10 (sunos 5.10) as the open-source opensolaris project, creating, with its forks, the only open-source (albeit heavily modified) system v implementation available. after oracle took over sun, solaris was forked into proprietary release, but illumos as the continuation project is being developed in open-source.