I personally think that a sign of a healthy technology platform is one where some people can make money from it, while the platform itself remains open. To use Linux as an example, it's wonderful that it's open source, and it's great that Red Hat can be a profitable company based on Linux. It's a good sign and it helps the Linux ecosystem thrive due to RH's contributions.

For Lemmy there are plenty of free apps - no-one is being forced to use Sync. I'm happy to pay for something that provides some more polish to my Lemmy experience, and doesn't require anything of anyone else.