What I think is significant part of the itch culture, is that it is pretty dense with creators and creativity, for example with the game jams movement. It clearly addresses people who are developers or active participants, not just passive consumers. That is quite awesome. It feels very different to simply waiting until you can buy something. Creators and artists, have some fondness for the open source technology, I think, because it simply makes it easier for them to bring forth their ideas. I respect open source culture, but again, if someone wants to make money, this is not going to be their place. Understandably, there is also very limited amount of time and effort an activist can invest in non-profit activities, therefore, open source developers need to work smart.
Modding is nice, but to be done right, it is not easy to arrange. Here is a quotation of a comment by @boranrobert, on the Mindustry game:
1) Modding idea is fantastic, but it can create large problems for future versions [of the game[ if not carefully designed.
2) Really good modding must have a very well organized structure, documentation and functionality (one external robust tool to create mods is a good start).
3) Modding is really fun until everyone decides to make their own external tool to create mods (this creates chaos and problems for future mod developers).
4) Modding distribution and creation must have from the beginning a simple dedicated web page (here you have everything - how to make mods , sharing mods, mods library).
5) Modding should include clear and robust API used by all modders (this is hard and complex to handle but it is essential).
6) Making mods should be easy to get into and hard for changing gameplay feeling.
To summarize, modding is both an opportunity and a danger - opportunity to expand the game and danger, for making it chaos and possibly falling into conflict with the status quo, in particular where some mods would claim supremacy over basic version of the game, thus splitting the community between those playing the "proper" version of the game and those playing the "vanilla".