I use TrueSTUDIO, professionally, which uses Eclipse. I’m looking to see if installing Defold with another version / instance of Eclipse would cause problems with either or both instances of Eclipse. I.e. if there is some common area that an Eclipse install uses then it might alter my TrueSTUDIO settings.
Any info appreciated 
I believe if you install the latest Defold editor(Editor 2) there would be no problems. I am almost positive that it has no correlation with Eclipse like the first version.
You can get it here: https://www.defold.com/editor-two/
Editor 1 is Eclipse based but there will be no conflict with other installations of Eclipse.
I’d recommend that you use Editor 2 though as we’ll be deprecating the old editor soon.