This can be extremely complex. There is a lot of legislation around the world that impinges upon or encompasses the idea of a volunteer - someone who freely offers to do something - in an organisation of some sort.
I volunteer for many different purposes so I've experienced many ramifications and observed many others. The difficulty discussing them is that legal jurisdications are so different. Even in the English-speaking world you can't assume that basic assumptions apply even within states/provinces of the same country. I could go into detail for New Zealand where I live but much of what applies for volunteers here is markedly different even in Australia, which is normally the closest match to us.
So I'm discussing this the legal ramifications in general areas with a few examples -II've edited it to make it clearer:
1. Volunteers can have a variety of statuses at the same time.
Generally, the various statuses are confusing because they often appear contradictory. Looking at "employee" status this is easy to see. A volunteer might be considered an "employee" for fringe benefit tax purposes - e.g. the organization pay tax for a benefit the volunteer receives - but not for income tax purposes - i.e. the volunteer is not considered to be an employee as they are not paid anything directly so they no taxable income.
2. The act of volunteering nearly always creates legal obligations that are not voluntary.
This is an irony, and sometimes a tragic irony too, because volunteers are often ignorant of the obligations that come with their role. An example is a volunteer being treated as an employee for workplace safety purposes. They also have to ensure that they don't create hazards in the workplace. They might even have to go on exactly the same training courses as paid, full-time, permanent employees. Volunteers are also exposed to many legal hazards as organisers of public events like races (including running, cycling, triathlon, automobile rallying, orienteering) have found out.
Just because we're talking about this in online communities doesn't mean that we avoid all those issues. There's some relevant statutes regarding online bullying and discrimination, for example.
A partial list of obligation and statuses
The obligations often align with the various legal statuses so I've tried to cover both in the one list:
Tax - mainly regarding monetary and non-monetary benefits but also covering volunteer expenses. The diversity of agreements and financial arrangements is amazing. As others have already said, what you do or use can impact the employee or tax status:
- Agreements - any understanding or arrangement. These are commonly the case for volunteers but knowing when they change to contracts is important.
- Bargains - an agreement to exchange something for something else, often for less than the usual monetary value. A bargain could be a promise to commit time voluntarily in exchange for, e.g., the role, status and abilities of moderator in a forum.
- Contracts - specific types of agreements enforcable by law. They aren't usually used for volunteers but you should be aware when your agreement can be considered a contract. Even if the volunteer does not become an employee, there are situations where they can be treated the same even if there was no intention to pay them.
- Benefits. Many volunteers benefit from their own voluntary work. Examples are religious communities (e.g. churches), sports clubs, many hobby clubs and societies, charities (e.g. when a family member is involved, has the same disease or whatever), and play centres (shared child-care facilities). They aren't usually taxed but you should check whether you could be.
- Pecuniary gain - a gain in monetary value is often the main reason for changing status. This does not mean that you have to be paid directly as the value of a gift can be sufficient to change the tax status of a volunteer.
- Perquisite (perk) - a benefit from holding a position such as in the above example of gaining additional capabilities as a forum moderator. A volunteer in a thrift/op shop often gets a "staff" discount just like an employee. The monetary value of perquisites may be taxed as fringe benefits but personal tax bills can also result.
- Fringe benefits are usually non-cash benefits. A rescue organisation, such as civil defence or fire fighting, may pay for gym memberships for their volunteers to keep fit. Any tax on fringe benefits for volunteers is normally paid by the organisation rather than the volunteer. While they may not be treated as employees it can be another stepping stone towards that happening.
- Honoraria - a payment made from moral obligation rather than legal obligation. Commonly honoraria are given for professional services ((e.g. by a lawyer, accountant, engineer, doctor, etc.) originally provided for little or no charge. Honory work is often performed with legal protection from some of the more expensive legal requirements of the profession.
- Reimbursement of actual expenses.
- Reimbursement of nominal expenses - I can't remember the actual name for this. For example, claiming your travel using standard mileage rates. Another example, I get a fixed payment, if I claim it, for facilitating a training course. The amount covers administration costs (like postage, pens and stationery), travel and telephone. There is a scale based on the number of course participants. The amount is set with the agreement of the tax authorities.
Employment. See the example above for taxes such as fringe benefits. Another example is whether expenses covered and benefits for a volunteer are significant and regular enough. Benefits can be treated as schedular payments just like regular pay packets. Then you might be treated as an employee or internal contractor, or even an external contractor. This decision partly depends upon your employment and contracts with other organisations. The tax status of employees and contractors is different as can be the calculation of expenses claims and how much can be claimed.
Profession. Professional organisations often have legal protections and obligations. There are many professions including chartered accountants, architects, professional engineers, and so on. As mentioned above, when professionals volunteer professionally they may need additional legal protection such as liability insurance. It has happened that professionals have offered advice as volunteers which is later considered to be professional services. So disclaimers, waivers and limitations of liability may also be needed to protect the volunteer and the organisation.
Unions. Many union delegates in the workplace are volunteers. If you perform a similar voluntary role then you may find your community being treated as a union. In many countries unions have to be state registered.
Health and safety. Workplace health and safety is primarily the responsibility of the organisation and secondarily of each individual. Specific occupational health and safety obligations often apply by trade/profession or workplace type. Just being there can be sufficient to have to comply with the obligations. If you don't then there may be a personal and organisational penalty such as a fine. For example, not wearing hard-hats in a construction zone can incure fines in many countries.
Insurance and worker compensation schemes. New Zealand has an Accident Compensation scheme that subsumes the right to sue for personal injury. It covers work and non-work injuries and allows compensation claims for injuries incurred while volunteering. A voluntary organisation or "industry" may have to contribute to the scheme if their volunteers have enough accidents to be on the radar.
Human rights obligations often apply in specific circumstances. An example is recruiting other volunteers which often means having to comply with statutes designed to protect prospective volunteers from being discriminated against. They don't take any account of volunteer status.
Religious membership often has its own set of laws for employees who are "called' to serve. This can include volunteers in roles who live on "by faith" (on donations). Also for volunteers who live in communities like monasteries/convents for monks/nuns. They may own nothing and get paid nothing but benefit from all their living costs being covered.