The speaker proposes that small companies can finance open source projects by contributing 1% of their income to a project of their choice. They argue that with over 23 million small companies in the European Union, this could raise substantial funding for open source. The speaker also discusses the importance of easy payment procedures and legal proof of payment for companies to donate to open source projects. Finally, the speaker emphasizes the need for financing maintenance work and infrastructure in open source projects, which is often overlooked.