Some top alternatives to Mattermost includes mi.team, Rocket.Chat, Glip, Zulip and Teamwork Chat.
Yes, Mattermost provides API.
Yes, Mattermost provides a mobile app.
Mattermost is located in Palo Alto, California
Mattermost offers Free Trial, Freemium, Subscription, Quotation Based pricing models
The starting price of Mattermost is $3.25/User/Month