You still own the code you release under GPL. the restriction you are describing is actually caused by the non-copyleft licences you claim to prefer. If you choose to use MIT, you are limiting which libraries you can use. If you had picked GPL to begin with, you can use any library.
If the exclusive ownership of something, in order to sell it, is the primary choice driving factor of a project. Then you should just make it proprietary. Anything else would limit your margins, since someone else can just fork your project, change it and make it proprietary themselves. A dual license is sometimes used in this case as well.
You still own the code you release under GPL. the restriction you are describing is actually caused by the non-copyleft licences you claim to prefer. If you choose to use MIT, you are limiting which libraries you can use. If you had picked GPL to begin with, you can use any library.
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If the exclusive ownership of something, in order to sell it, is the primary choice driving factor of a project. Then you should just make it proprietary. Anything else would limit your margins, since someone else can just fork your project, change it and make it proprietary themselves. A dual license is sometimes used in this case as well.
You can sell GPL licensed software. You don’t have to publish the source code publicly online.