It's nothing like donations: people pay these extensions / apps like any other paid software. That's my point, actually.
In XWiki's case, we know it's not perceived like "I could be having it for free but I'll pay anyway because it's a nice thing to do".
We do explain that our stuff is open source to our customers though. It's a selling point.
In our case, admittedly, it helps that our target customers want our support anyway.
> before someone just undercuts you with a fork.
Absolutely, it is a risk to take into consideration. Now, maintaining a fork has costs too, and someone doing this would rely on continued maintenance and goodwill from the upstream vendor as well.
Downstream vendors actually have an incentive to keep good relationships with upstream, so they can share fixes and have some guarantee that whatever they base their business on keeps being maintained.
In XWiki's case, we know it's not perceived like "I could be having it for free but I'll pay anyway because it's a nice thing to do".
We do explain that our stuff is open source to our customers though. It's a selling point.
In our case, admittedly, it helps that our target customers want our support anyway.
> before someone just undercuts you with a fork.
Absolutely, it is a risk to take into consideration. Now, maintaining a fork has costs too, and someone doing this would rely on continued maintenance and goodwill from the upstream vendor as well.
Downstream vendors actually have an incentive to keep good relationships with upstream, so they can share fixes and have some guarantee that whatever they base their business on keeps being maintained.