I considered merging #contracts and #sdk into an Open Source category, but didn’t see enough difference between this new category and #general.
Topics in the forum are predominantly general discussions or support questions, having categories that match this breakdown, I believe, would make things simpler for the community. A topic is generally going to be either a support question or a discussion.
Whilst merging is non-trivial, #contracts and #sdk categories only have 50+ topics each.
The way I see it, General is open to discussing smart contract development in general, potentially using OpenZeppelin libraries. On the other hand, this #opensource category would be specific to discuss the development of the OpenZeppelin tools themselves. Nevertheless, given that it's not super active today, I'd push for adding it as a subcategory of General. And I'd definitely consider a different name instead of #opensource.
Maybe a good name for the hypothetical #opensource category would be #internals. The Rust community uses this name for one of their forums (the other one is “users”). Do you think that name would make the difference clear enough that it wouldn’t hurt to have as a third category?
That said, I would be okay with merging it all into #general!