Aratoi Regional Trust Board acting chairman Frazer Mailman said the agreement was based on "commitment to mutual and good faith co-operation".
It reflected Aratoi's importance in the community and the need to reassure those who funded the museum the organisation was in good hands for the future.
Mr Mailman, along with Friends chairwoman Penny Bunny and Foundation chairman Bob Francis, recognised "past tensions" between them had not been in Aratoi's interests.
Members of all three organisations were now committed to constructive, open dialogue an to looking at and resolving issues, he said.
This month's meeting will look at producing a joint newsletter.
Meanwhile the appointment of a "person or persons" to replace Mr Boroughs will be led by the trust board and will include iwi input on the selection panel.
The trust board has resolved to keep the other parties fully informed of its deliberations during the appointment process.
The three organisations have also agreed to a disputes resolution process.