There are several contributors on the market of open source: volunteers, Linux distribution companies, companies with a single open source program as their main product, hardware vendors, end-user businesses and their contractors, service businesses, government, academic and scientific researchers. The synthetic comparison of the actors is to be found in the appendix section. 
i. Volunteers – this activity starts from a hobby and it does not imply a financial motivation. It gradually becomes volunteering.
ii. Linux distribution companies – they work mainly as integrators of the work of others, they do a lot of maintenance work in order to eliminate bugs for their paying customers and they do original open source software development to enable their product or a new market. Today we are experimenting the second generation of open source business plans: some Linux distributions are trying to imitate proprietary software. Behind their costly box of software or per-seat license is a product that the customer could acquire without charge through other channels. The best name for this business model is proprietary open source, as services are offered but the business is operated in the proprietary box-software model. It is important to emphasize that not all Linux distributions engage in proprietary open source, and that proprietary open source is not the dominant business model for open source software development (ex: Red Hat, Novell).
iii. Companies with a single open source program as their main product – these can be of three types: mixed open source and proprietary licensing model (My SQL AB, Sleepycat Software), a core open source program with proprietary software accessories (also called widget frosting, ex: Sendmail Inc.), pure open source plus services model.
iv. Hardware vendors – they produce open source because there is no conflict between open source and differentiation for them as there is in a software company. This activity enables sales, does not reduce their hardware-based business differentiators and thus it does not threat the profit centre (ex: IBM, HP).
v. End-user business and their contractors – their contributions come from the internal software support and development staff, or contractors supporting the company (ex: eBay).
vi. Service businesses – they participate in the development and maintenance of open source programs, but not intensively in any one.
vii. Government – it provides services that enable economic and social activities.
viii. Academics and scientific researchers – they are usually graduated. In science the maxim is publish or perish and it holds true for open source as well. To be considered valid, scientific research has to be capable of being duplicated. Some research work is performed by unsalaried students.
 See Appendix no. 7 for a comparison