I'm thinking about building a website that has the word 'tweet' in it's domain name. It will be using twitter API.
I'm not sure if the word 'tweet' is trademarked, I didn't find any solid results on google, except of some old results where twitter were suing about on these matters from 2011.
I came up with this post because I'm facing exactly the same issue as you, I don't know what you did at the end, but if anyone else has this same issue, I've found a blog post of the Twitter's co-founder, and he says clearly that they won't go after anybody who uses the word "tweet" as long as they don't use it in a "confusing or damaging project".
Here is the blog post: https://blog.twitter.com/official/en_us/a/2009/may-the-tweets-be-with-you.html
So I'll keep building my SaaS with tweet in its domain name.
It's trademarked. http://tmsearch.uspto.gov/bin/gate.exe?f=doc&state=4809:zxl77r.3.1
You could reach out to them asking for permission to use it.
I noticed all companies that had the word 'tweet' in their names changed their name years ago. Seems that twitter is a very (legal) aggressive company, since the co-founder said once they won't pursue companies with the word 'tweet' in their names.
I don't think I will pursue this.
Can you share any resource that you found on the topic? I'm currently in a similar situation.
good luck with other ventures!