In the early days opentext.org used Codex Sinaiticus to avoid copyright restrictions with the German Bible Society (http://www.opentext.org/resources/articles/a1.html). But when I look at the Logos information window for this resource, it says the Greek New Testament text is copyright 1993 Deutsche Bibelgeselschaft. This is the date of the UBS4/NA27, so I am guessing that opentext.org uses one of these now. Can someone confirm which one it is or if it is still based on Codex Sinaiticus?
Also, it is interesting that the Logos information window for the NA27 says copyright 1998. I assume this is because the used the third printing of the IBS4 as the basis for the electronic edition.