The original concept album (on which the stage and film versions are based) was deliberately ambiguous about whether Jesus was, in fact, anything other than a man. Andrew Lloyd Webber and Tim Rice came to the Gospel text with a humanistic premise.
"We approached the opera from the point of view of Christ the man, rather than Christ the God," Rice noted. "We had been well-coached in the mechanics of Christianity and its legends and beliefs. That was drummed into us at school. They treated the legends, so we decided to treat the bloke as a man. We read the gospels very carefully and that was it. What we did not read was eighty-three other people's interpretations of Christ because we didn't want to be affected by their views. We stuck to the text and our interpretation of what we think could have happened." [...] "We tried to humanize Christ, because, for me, I find Jesus as portrayed in the gospels as a God as a very unrealistic figure." 1
"We were basically trying to tell the story of Christ as a man," says Tim Rice. 2
Note that the title song Superstar, in which Judas questions Jesus about his actions and motives, was the first one to be written: the rest of the opera is built around it. That certainly comes through in the way that the two creators talk about the work - it's all about that central accusation.
Rice and Lloyd Webber could not agree about how to handle the resurrection:
Webber has been quoted as saying that he and Rice had arguments, "long arguments, in fact, about the basis of the opera and how it should be treated. We had to decide which events in the life of Jesus we were going to write about - and this was the most difficult area of all in which to find agreement. Eventually we chose the last seven days of His life. Even now, I don't go along with some of the things that Tim has written in the opera. The lyrics are extremely good for any composer to work with, but I don't necessarily agree with all of them. I would have liked to have included the resurrection, but it just wouldn't have been worthwhile. We disagree too much about it." 1
Accordingly, the ending of the opera was deliberately made to be open to multiple interpretations, which might be brought out differently in various stage or film versions. For example, regarding the 1971 Broadway production, Rice said:
"I think O'Horgan's production hints more strongly at the resurrection than the record does. The reaction of the crowd below [the cross] - going from hysteria to chaos to a beautiful sort of peace. O'Horgan is saying, 'This is not the end.'" 1
The fact that the stage version will invariably end with Jesus coming back for a curtain call - effectively a resurrection! - also changes the way in which the story is perceived, compared to a film adaptation.
For the 1973 film, director Norman Jewison broke with the two original creators, who had a different opinion about how the movie should be approached. The fact that his film does allow space for a resurrection may spring from his slightly different take on the original text, and the context in which it was made. His idea was to present the events on a human scale (no huge crowds), blurring temporal lines (neither modern dress nor period authenticity) so as to suggest parallels between attitudes then and now. He was also conscious of the possibility of religious offense, especially given that the picture was being filmed in Israel (actually at the same time as the massacre at the Munich Olympics) and previous versions of Superstar had been heavily criticized for anti-Semitism. All of this may lead to a slightly more sympathetic and open-ended view of the story, compared to the accusatory tone of the original libretto. 1
The Gale Edwards version (originally also a stage production in 1996) was made partly because Lloyd Webber himself was dissatisfied with the 1970s productions, and wanted to stage a show that was more true to his own image of what the opera text was about.3 By this time, he had a lot more clout than he did in the early 70s, when he was unable to stop the Broadway and film directors from doing their own thing. 1 Whereas the original album was a compromise between Lloyd Webber (agnostic) and Tim Rice (self-described as "slightly religious"), this version is a purer strain of Lloyd Webber. He is probably not making a particular theological point so much as a dramatic one, thinking the spectacle and the experience would be improved by presenting it in this way.3 A sudden stop is not necessarily saying that there is no more to the story, but it does perhaps startle the audience into thinking about it in a way that a tidier ending might not.
I did not find any direct reference from Jewison or Edwards about their artistic choices, but I do think that what they did was fairly subtle, within the range of interpretations supported by the ambiguous opera text. Essentially, being true to the original vision of what the opera is about means not coming down too firmly on one side or the other. That said, some productions - particularly those sponsored by churches - have added an explicit resurrection scene or song at the end, which certainly counts as making a theological point. 1
1. Rock Opera: the creation of Jesus Christ Superstar from record album to Broadway show and motion picture. Ellis Nassour and Richard Broderick. Hawthorn Books, 1973.
2. Life magazine. May 28, 1971.
3. Billboard magazine. Oct 19, 1996.