There certainly isn't a need for Sun Grid Engine as it was officially renamed to Oracle Grid engine. The copyrights were then sold on to Univa who produce another fork called Univa Grid engine. The long term supported path for Oracle Grid Engine is therefore an upgrade to Univa Grid engine. I disagree that the first two tags say that 'The tag is used incorrectly or ambiguous'. I'm pretty sure that most people who use the sge tag are using it as a generic term because that was the name it had before grid engine started forking. They should merge because they're both de facto generic.

While Son of Grid Engine does use the SGE abreviation my impression is most people use it more generically to refer to all of the various forks.