[ProblemFactory]

Having a premium product could also mean that the open-source version grows faster.

Having stable revenue means the ability to spend 100% of the time working on the project (instead of it being a side project), and hire more full-time employees. It is possible that as a result both the pro and open-source versions improve faster than in an only-volunteer open-source project.

[troels]

That's a good point. Although, so far, the project has evolved pretty well, so it doesn't seem to remedy a current problem.

An alternative strategy to ensure it to do so in the future, could be to build a team of open source contributors to take charge of the further development of the project. As a user, I would prefer this, as it doesn't have the inherent conflicts of interests that a premium/free model has.