Hamas's Charter is a bloody document that calls for the destruction of Israel and the murder of Jews. It considers all of the Palestinian Mandate, including Israel, to be part of an Islamic waqf, and no one has the right to give up an inch of this territory for peace. I have discussed Hamas's Charter in much more detail here.
What is less well known, at least in the United States, is that Hamas has shown signs that it may be willing to modify its charter under the right circumstances. Certainly, there appears to be a division within Hamas as to whether the Charter could be modified, but it is important to recognize that the potential to peacefully persuade Hamas to modify its Charter exists. Or at least it existed before the current war in Gaza. It is uncertain whether the war will soften Hamas up and make them more willing to modify their Charter, or if it will harden their attitude and make a peaceful evolution more difficult.
In any case, it is important to know about signals Hamas has sent out about its flexibility to change. Seth Ackerman from Fairness and Accuracy In Media wrote an important report detailing Hamas's signals about eight months after its October 2006 election. YOU SHOULD READ THE WHOLE REPORT, but since it is long I will present you with some of its highlights.
Yet analysts also saw the potential for far-reaching change in Hamas’ political outlook. As early as 2000, a study by Israel’s leading academic specialists on Hamas (Shaul Mishal and Avraham Sela, The Palestinian Hamas) cautioned that the Islamist group, despite its fanatical image, 'is not a prisoner of its own dogmas. It does not shut itself behind absolute truths, nor does it subordinate its activities and decisions to the officially held religious doctrine.'" . . .
Yet as Mishal and Sela observed, the group possessed a deft “ability to justify controversial political conduct in religious terms” and a “willingness to exist with internal contradiction.” The scholars’ conclusion: “We cannot rule out the possibility of a significant shift in Hamas’ relations with Israel to the point that what seems ideologically heretical in the present might become inevitable in the future.” . . .
More importantly, the group had begun to signal that it was ready to adjust its political position on the conflict with Israel. “Slowly, painstakingly, but inexorably, Hamas is moving away from its traditional notion that Palestine is an Islamic waqf [land-in-trust] ‘from the river to the sea,’” observed the Economist’s veteran Palestine correspondent, Graham Usher (Middle East Report Online, 8/21/05). The party had not simply reverted to a strategy of “a long-term armistice (hudna) that would accept the ‘1967 Territories’ as a Palestinian proto-state until the forces of Islam are strong enough to recover Palestine ‘as a whole.’” Rather, Usher reported, “Hamas is signaling that it accepts Israel as a political reality today and is intimating that it would accept a final agreement with Israel ‘according to the parameters of the  Madrid conference and U.N. resolutions,’ says Palestinian analyst Khaled Hroub, an authority on the Islamist party.”
Just before the election, Robert Malley, the former Middle East policy director in the Clinton National Security Council, organized a report for the International Crisis Group (Enter Hamas: The Challenges of Political Integration, ICG, 1/18/06) that reviewed the “signs of pragmatism” coming from Hamas. Based on dozens of interviews in the field with officials from Hamas, Israel and elsewhere, the report observed that, “far more than Fatah, Hamas has proved a disciplined adherent to the cease-fire, and Israeli military officers readily credit this for the sharp decline in violence. In recent statements, Hamas leaders have not ruled out changing their movement’s charter, negotiating with Israel or accepting a long-term truce on the basis of an Israeli withdrawal to the 1967 lines.” Underlining the depth of Hamas’ ideological shift since its charter was adopted in 1988, the paper judged that “today, their electoral platform is in these respects closer to Fatah’s outlook than to Hamas’ founding principles.”
Perhaps the single most knowledgeable observer of Hamas in the West is Alastair Crooke, a former British intelligence officer who served as liaison to the Palestinian National Authority for the European Union from 1997 to 2003 and worked closely with CIA director George Tenet. In a private policy paper distributed to E.U. officials at the time of the January elections (cited in UPI, 2/2/06), Crooke wrote that Hamas’ growing willingness to support a comprehensive halt to violence and negotiations with Israel leading to two states represented an unprecedented opportunity for peace, since, unlike during the Oslo years, “the results of such talks would actually be implemented by a disciplined movement with a mandate from its own people”—i.e., Hamas. Such a deal “offers the best chance for an enduring settlement” with Israel, Crooke judged. . . .
There is no need to sugarcoat Hamas’ history of brutal tactics or its bellicose ideology. Its activists continue to rouse their supporters with messianic rhetoric pledging to pursue the battle against Israel until total victory is reached, and in its armed attacks across the Green Line the group has seldom made the slightest effort to distinguish innocent civilians from soldiers. But the characterizations of Hamas’ stance toward Israel quoted above range from incomplete to misleading to flatly wrong.
Hamas’ leaders are not of a single mind. They include both fiery radicals who dismiss any suggestion of co-existence with Israel and moderates whose views differ little from those of Abbas, a Fatah leader who is considered a moderate. But over the months and years preceding January’s elections, the center of gravity within the group’s thinking had unmistakably shifted. Senior officials repeatedly signaled that Hamas is open to changing its policy in favor of a long-term peaceful accommodation with Israel; that it is willing to take concrete steps toward this goal, provided that Israel reciprocates; and that it would seriously consider moving even further given the right political circumstances. . . .
Yet in almost every case, the U.S. media failed to broadcast these signals. For instance, four months before the elections, a moderate Hamas candidate representing Nablus, Mohammed Ghazal, told Reuters (9/21/05) that the group could change its 1988 charter calling for Israel’s destruction and that it was open to negotiating with Israel. “The charter is not the Koran,” Ghazal said. “Historically, we believe all Palestine belongs to Palestinians, but we’re talking now about reality, about political solutions. . . . The realities are different.” If Israel reached a stage where it felt able to talk to Hamas, Ghazal said, “I don’t think there will be a problem of negotiating with the Israelis.” (Less than a week after Ghazal’s comments, Israeli soldiers raided his apartment and arrested him—AP, 9/27/05.)
Asked about the charter the following month, a leading Hamas hardliner, Mahmoud Zahar, told Ha’aretz (10/26/05) that “no one is thinking now about changing the charter, but in principle it is not impossible.” . . .
By spring 2006, it seemed clear that the group was open to almost any solution that did not cross the red line of recognition of Israel by Hamas as a political party. As one Hamas leader (Hamas MP Riad Mustafa, ICG report, 6/06; emphasis added) explained:
I say unambiguously: Hamas does not and never will recognize Israel. Recognition is an act conferred by states, not movements or governments, and Palestine is not a state. Nevertheless, the government’s program calls for the end of the occupation, not the destruction of Israel, and Hamas has proposed ending the occupation and a long-term truce (hudna) to bring peace to this region. That is Hamas’ own position. The government has also recognized President Abbas’ right to conduct political negotiations with Israel. If he were to produce a peace agreement, and if this agreement was endorsed by our national institutions and a popular referendum, then—even if it includes Palestinian recognition of Israel— we would of course accept their verdict. Because respecting the will of the people and their democratic choice is also one of our principles.