In 2005, Donald Fisher, a billionaire retailer and one of the world’s most prominent art collectors, telephoned the head of the San Francisco Museum of Modern Art. He had a simple request: “I want to come see you.”

“He had the idea,” recalled Neal Benezra, director of the museum then and now, “that maybe, together, we could develop what I suppose would have been called the Fisher Wing.” The proposed museum addition would house the fabled collection of contemporary art Fisher had built with his wife, Doris, over four decades.

“I thought about it a lot,” Benezra said in a recent interview. “What Don was offering was, on the one hand, extremely generous … but Don wanted something that I felt we couldn’t offer him ... a kind of curatorial control over what got shown.

“I felt that, as generous as this offer was, our integrity would be at risk,” Benezra said, “because the museum really needs to control, from a curatorial point of view, if nothing else, how art is presented in our building.”

The executive committee of SFMOMA’s board of trustees, after some discussion, agreed and turned down the offer. That set off a controversial, multiyear effort by the Fishers to build their own museum in the Presidio, which ultimately fizzled. As Donald Fisher’s health failed, a new deal was struck with SFMOMA, resulting in the extraordinary new building opened by the museum this year. At its core: the Doris and Donald Fisher Collection Galleries.

So, just what was the new arrangement reached in 2009, shortly before Donald Fisher’s death? Does it serve the museum’s mission, and the director’s determination to preserve its integrity? And more to the point of our interests as museumgoers, how does it shape our understanding of art and art history since 1960?

The short answer is, we don’t know. And the museum, so far, is trying very hard not to say.

When SFMOMA announced in September 2009 what it called — all in a single news release — “this groundbreaking partnership,” “this extraordinary partnership” and “this unprecedented collaboration,” one thing was clear: The museum was not receiving a gift, in the normal sense of that word.

At first, a trust was to be created and co-administered “to oversee the care of (the Fishers’) collection at the museum for a minimum of 25 years.” A few months later, it was announced that the deal had expanded to “a period of one hundred years, which will be renewable thereafter.”

Beyond the platitudes and the contract’s length, though, little information was shared. Some prying I began doing in April, before the expanded museum opened, dislodged the fact that a grouping of Fisher collection works must hang together in the galleries once every 10 years. But a request for more details, including a look at the loan agreement, was repeatedly avoided or ignored by the museum’s public relations team.

As a private, nonprofit institution, SFMOMA is not technically required to release such information. But even basic facts, such as when the loan term ends, were not forthcoming — until the museum learned this story was planned.

We now know a bit more. Much of it is benign: The loan term ends in May 2116, for instance, and is renewable in increments of 25 years.

But some of the agreement’s details cause some concern for SFMOMA’s sake. For example, though Benezra and his staff refer often to “the Fisher family” as the museum’s partner, most of the art, in fact, belongs to Doris Fisher alone, and the museum’s partnership is with an entity called the Fisher Art Foundation.

A 2013 federal income tax filing, the most recent available, lists Fisher and her three sons — including Bob, who is president of the SFMOMA board — as the foundation’s only trustees. That filing lists its art assets as worth $15,600,000 — a paltry fraction of a collection that contains single works worth that and more. Bob Fisher declined to be interviewed for this story.

Benezra professes great confidence in the quality and depth of the relationship between the family and the museum, and I see no reason to doubt his judgment. But when pressed, he told me, “If Doris has loaned a picture from her home, she might like to have it back, and we would certainly give it back to her at the end of some period of time. Once they go into the foundation, however ... they can’t have any private use anymore.”

The museum ultimately told me that, of the 260 works currently on view, only five are still privately held and are scheduled to be returned. But it refuses to say what, exactly, is in the collection beyond those 260 objects, or how many of the other 835 or so pieces said to be part of the deal belong to Doris Fisher personally. It did say that “works are being transferred at the Fishers’ discretion, in due course, over time, from the private collection to the foundation collection.”

The major question that leaves hanging, of course, is what objects Doris Fisher might someday want returned to her. One work or two might have little effect on the overall collection; but what if she, or some heir in the decades ahead, asks for hundreds of works back?

While that could put a crimp in the museum’s long-range plans, other aspects of the partnership recently unearthed appear to be far more disconcerting for us, the audience.

It turns out, for instance, that the once-a-decade schedule for showing the collection in what Benezra calls a “monographic” presentation is the tip of a much deeper iceberg. Those huge galleries on the fourth, fifth and sixth floors that carry the Fisher name? Unlike in other spaces designated to honor big donors, which might hold a range of different works and exhibitions, the Doris and Donald Fisher Collection Galleries are required to contain primarily Fisher works at all times. No more than 25 percent of what is on view may come from other lenders or donors.

This stipulation has major implications. It means that something like 60 percent of SFMOMA’s indoor galleries (not counting free-admission areas that serve as combination lobby and exhibition spaces) must always adhere — or, at least, respond — to a narrative of art history constructed by just two astute but obdurately private collectors.

Granted, curators will be able to address some of the collection’s most significant absences (the Fishers tended toward big art by men of European, particularly German, heritage). But for the next 100 years, their job will be limited in those galleries to a kind of scholarly embroidery, filling in around the edges of a predetermined scenario with works by other artists, such as women, artists of color or California artists.

It might be better to simply accept that the Fisher collection has its own logic, and make a full-throated argument for other interpretations elsewhere in the museum.

Another constraint of the deal: a requirement that any loans of Fisher works to other institutions be approved by the Fishers.

What we see in art museums is the art of the rich.

One of the main reasons we visit museums is to engage directly with works that are rare, fragile and generally unavailable outside secure institutional walls. Especially in the U.S., where museums depend heavily upon donations, these valuable works come from wealthy contributors. Without their generosity, our cultural heritage would be closeted away, and our communities greatly impoverished.

Yet museum audiences expect their visit to be at least in part an educational experience, and virtually all museums see interpretation and education as key aspects of their mission. Curators and museum educators are charged with meeting that need, and we have a right to assume that the choices they make are based, above all, upon their training and experience. (And let’s be honest: Another part of their job is to shelter us, if need be, from the arrogance of the successful and the wellborn.)

Museums like SFMOMA that show contemporary art, in particular, face a thorny problem. The number of artists in the world is vast, the number of works seemingly limitless. The choice of what is exhibited, even temporarily, is a signal to the audience. Including a work of art in a permanent collection, with all the costs of housing and care, is laden with even more significance. Before a single word of text is affixed to a gallery wall, explicit and subliminal messages are conveyed through the selections made, their placement and juxtaposition, even choices such as wall color, path of viewing and relative scale of objects and room.

Single donor-focused museums and galleries have existed for a long time. In the U.S., one thinks of great museums like Boston’s Isabella Stewart Gardner Museum, the Barnes Foundation in Pennsylvania, New York’s Frick Collection, or the Metropolitan Museum of Art’s Robert Lehman Collection. All are tightly restricted with respect to what is shown, loaned and borrowed, and even how their works are displayed.

These institutions and subcollections present themselves clearly as the vanity productions they are — even as they reveal to us essential aspects of our cultural past. When we visit them, we know that we are seeing art through a particular lens. SFMOMA has yet to be that transparent about its presentation of the Fisher collection.

Moreover, a museum that professes to be, as SFMOMA’s mission statement claims, “a dynamic center for modern and contemporary art,” must take a wider view. Headed into a century-long arrangement, the museum, founded in 1935, has not yet passed its first 100-year mark. The practice and propositions of art have shifted profoundly over its first eight decades; accordingly, the museum has adapted to those changes on a continuing basis, just as artists, critics and the audience have had to do. But if a core collection display is frozen in a certain time, tied to a prescribed point of view, how does the museum stay current, much less maintain its longed-for dynamism?

These are not matters of legality or ethics; rather, they are concerns that grow out of the institution’s commitment to serve its community. It goes without saying that any museum in the country would have reshaped policy and made extraordinary accommodations to land the Fisher collection. Based solely on the works now on view, it’s clear that SFMOMA is able to share original objects that can be experienced in no other museum, revealing aspects of the history of recent art that no one else can. As a result, it plays a role on the world stage today as one of the great museums of contemporary art.

But with the place it has carved out as trusted guide to the art of our time comes accountability. In an environment of secrecy and tight-lipped, lawyerly communications, we are left to speculate on where it plans to take us, and what new role its curators will play.

And, given the agreement as we now understand it, we are left with a question to which none of us alive will likely ever know the answer. Will the San Francisco Museum of Modern Art still be a great contemporary museum in 100 years?