I don't know all of them, but I can list a few. There are some possibilities: - Binaries: Some users will pay for precompiled software, so that they do not hav

I don't know all of them, but I can list a few. There are some possibilities: - Binaries: Some users will pay for precompiled software, so that they do not have to compile it by themself. You might find this sometimes in some "app stores". - Physical components: You might sell hardware, printed manuals, DVDs, etc. - Paid support: You can sell support to customers who want priority support and/or professional support. SQLite also has paid support, and in the case of SQLite, this paid support also includes testing. - Hosting: If you do not want to install and host it by yourself, the company that makes that software may do it for you, if you pay them to do so. - Dual licensing: Some software has dual licensing, such as Ghostscript and Swiss Ephemeris. SQLite also kind of does; you can pay for a license, even though you won't really need it (since it is already public domain), but it is there in case your company's legal department requires you to have a license. - Customization: If you do not want to make the changes by yourself, you may be able to pay them to customize the software for your use profesionally. - Proprietary components: I do not really recommend this for must cases, but it is sometimes a possibility. - Installation: Payment for the company that produces the software to install it properly, where the customer requires it.