I'll start with maybe I just don't know enough about open source. I do understand that the code is available and people can see it, make suggestions or adjustments, or essentially make their own thing using some or all of the code. I'm all for sharing things as necessary and learning from others when possible. With this though, I personally am on the side of: I trust ljdawson to do what's best for this app. I am on the sync train because of him the incredible app he made, and how he leads and interacts with the sync community.
I've been using Sync for about 7 years and I've always thought Ljdawson is very active with the Sync community and (from my experience) has been pretty receptive to feedback on his app. When the material you version of Sync came out, people didn't like it so he made it so you can choose between the material you look or the old look. There are tons of customization options. I feel very informed with each update as well as what his next plans are. There are paid features that both support him as a dev and the longevity of the app. He puts a lot of time and care into creating the product we get to use and for me that is more important than being able to access the source code.
I understand the worry for sure. My gut says that stems from the current situation at reddit, but I personally don't think the answer is sync going to open source. If something crazy happens with sync, there are (currently) other options.
open source projects still need approvals for merging into a protected branch.
In other words, if you were to open source a project, others can view the code or submit edits to the code on a new branch. Just the mainteners of the repository (you and who ever else you choose to have that power) would need to check that new code and approve it.
If they made a change you don't want to implement, you just deny the change and no new code is merged.
That person could then (depending on licensing) make a fork of your project that does have their change implemented. This means they would make an entirely new project and they would have the ability to make changes.
You would still have full control on the original project that you created. And no changes would be pushed to an app store.
TLDR: if something is open source, it only ensures it's longevity and resilience. Open sourcing a project does not mean now that it is changed at the will of the internet without the express approval.
That's helpful, thanks for the info!