Can't believe how spoiled we have become with open source. I see that a license purchase is required here and is immediately taken aback.
I am the author of a similar source available package and selling to developers has been such a painful experience. They (we) have one of the most privileged situations when it comes to finances but they are so reticent in buying software. It's not that the software might not be good, or might not help them, but "it should just be free".
That has been my experience. Since my indie developer endeavour, I changed the way I see other solopreneurs and their businesses.
Let's support each other through projects like these and these types of licensing and stop taking things for granted.
Quite often, some extra administration is required, just to ensure that a license is used correctly.
More recently, with subscription based pricing models, I find it very hard to determine the actual cost upfront. With free software this insecurity is not present.
Possibly the most important factor here is trust. With open source communities, I find it fairly easy to determine the quality of a product, and its development team. Commercial companies tend to hide their internal communication, making it harder to assess priorities and how problems are resolved.
I wonder if these issues could be solved by intermediaries.
The problem is not that the software is unfree (i.e. the software costs money), the problem is that the software is unfree (i.e. the license is proprietary).
Source-available software is usually not as flexible as free and open source software, because it has additional restrictions on how the code can be used or redistributed. When there are two software options with equivalent feature sets, and one is source-available while the other is FOSS, it makes sense in many cases to prefer the FOSS one for its more flexible licensing.
The main exception is if a developer is selling proprietary software and wants to incorporate copylefted FOSS in a way that would be incompatible with the license, in which case a custom licensing agreement (multi-licensing) could satisfy both parties.