Personally I've been using Linux and open source software for 20 years. I try to use and support open source software at every opportunity.

As for the rest of Nostr, it is still a tech/dev crowd. It is also rooted in the bitcoin community, where open source is seen as important obviously. In a community where freedom is one of the main selling points, I think software being open source will always be important. Don't trust, verify and all that.