A common solution to this is dual licensing. The project gets open sourced under a strong copy left license (ie GPL or AGPL). Then you offer a commercial licens

A common solution to this is dual licensing. The project gets open sourced under a strong copy left license (ie GPL or AGPL). Then you offer a commercial license for closed source usage. The downside is that this greatly complicates project stewardship. You can no longer accept contributions to the version you maintain without a CLA. Related, if someone forks you can no longer incorporate any of their changes unless you track them down and convince them to sign a CLA or otherwise license their changes to you. It should work well if you were already planning to do everything yourself. You get to sell your work while also allowing the open source ecosystem to benefit from it free of charge.