Sorry to be late in responding to this but the site has been down. Let me try to deal with the issues as I see them!
Ownership of the images/right to use
Warren should retain copyright in his images in my opinion as they represent his intellectual and artistic input. Since the organisation is a 'worthy cause' and he wishes that they are able to use the images for their promotional purposes, without cost or need to revert back to him every time they wish to publish something, there are a couple of points which need to be considered:
1) Warren retains copyright of the images, but grants to XYZ a licence, in consideration of the organisation providing the film and the processing of the images without charge to Warren, for use of the photos for uses directly connected with the organisation charitable principles (whatever they may be - it saves having to enumerate a whole list of things and the one that they want to use them for is missed from the list for example); providing that where appropriate, an acknowledgement of Warren as the photographer is made (it may not be possible or desirable in every instance). Each party undertakes to use their best endeavours in this regard - not watertight, but practical.
2. Warren undertakes to acknowledge the organisation XYZ in any published use of the photographs he may undertake, and further undertakes to use the photographs only in a manner consistent with the organisations principles. This may need polishing but the essence is that both need to assure the other that they are both free to use them, they acknowledge each other when they do, and they will only be used for appropriate purposes.
That's the easy bit!
The hard bit depends on where Warren lives and what the law says about liability etc etc. I cannot give any advice on this, see the disclaimer. If in doubt, see the disclaimer! General principles are as follows:
1. You cannot contract out of negligent events - if Warren inadvertently and negligently clips a child say with his camera, then he may well be liable for assault or damage or both. He may well be able to get coverage under the organisation's public liability insurance, he might have his own under a domestic or professional policy. This will depend on the terms of the policies. This is a complex area as it involves surrendering rights (subrogation) to the insurer in the event of a claim, and possible nomination on the policy etc etc etc. Warren should request the organisation to provide him with the benefits of any public liability insurance held by them, to the extent that they are able in consideration of him providing his services to them gratis.
2. There may be statutory provisions within his local jurisdiction which may help to limit his liability as a volunteer. Post 9/11 when insurance rates went North, some jurisdictions enacted legislation limiting the liability of volunteers and the like to reduce overall insurance costs, appreciating that many do not carry individual indemnity and public liability insurance. Here in Australia, most states and territories have enacted such legislation. It varies from state to state.
A letter along the following lines may assist:
"Dear
You have requested me to take photographs at the XYZ event on the 40th Doctober 2006. I am willing to provide my services to XYZ subject to the following provisions.
In consideration of XYZ undertaking to provide film and processing of photogrpahs taken at the event, I undertake to provide my services and necessary equipment free of charge, and will take suitable photographs at the event. I will retain copyright of these photographs, but grant a licence to XYZ to use any, and all of the images for their promotional and internal use, free of charge, provided that where possible and appropriate an acknowledgement of myself as copyright holder is given. This licence shall remain in effect until 43rd Febgust 2010, at which point it may be renewed by mutual consent.
I undertake only to use the images for my own purposes which are consistent with the XYZ's principles as provided in their Articles of Association.
In consideration of me providing my professional services to XYZ for this event, XYZ undertakes to indemnify me to the extent permitted by laws of the State of Nirvana for any acts, including negligent acts of commission or omission, but excluding any acts of gross negligence or deliberate intent committed by me, and will provide to me as a co-insured the benefits of any public liability insurances to cover any liability to third parties whether under tort or statute which I may incur as a direct consequence of providing my services to XYZ for this event".
I suggest that a draft of the letter be discussed with XYZ and used as an aide memoire before any final draft is agreed.
DISCLAIMER
The foregoing advice is provided on the strict understanding and undertaking that "hugivza" is not a legal practitioner, and recommends that legal advice be undertaken within an appropriate jurisdiction prior to making any commitments the subject of this advice, and further disclaims any liability whether under tort or statute within any competent jurisdiction to the extent permitted by law for such advice and any uses to which it may be put.
Suerte!