Since Master Calendar is an app and not an official view type, the sharing capabilities are somewhat limited.
Share the App via Link
It is possible to create a shareable link to the app by following these instructions: https://support.airtable.com/hc/en-us/articles/360057070593-Embed-and-share-individual-apps-beta-. Note: this feature is a closed Beta and may not be supported in the future.
Please be advised that this method will come with every table of the base visible underneath which users could get to by clicking a "show data" button in the top right corner. If this is unacceptable to you, I would not advise this method. There is the ability to lock the app share link with a password much the same as a shared view or base link, but you would still expose the full base to anyone with the link and password.
Workaround 1: Sync data to another Base
By syncing just the records and data you want displayed on your calendars to another base, using the above mentioned App Link won't expose extraneous data to outside users. I would recommend doing this if you have concerns with revealing the entire contents of your base to more collaborators or the public if embedded on a website.
Click here to learn about Airtable's base syncing feature: https://support.airtable.com/docs/airtable-sync-basic-setup
Note: this would likely require you to set up two instances of Master Calendar: one in your original base, and one in your synced base. Subscriptions to Master Calendar allow for unlimited installs, so you need not worry about added cost.
Workaround 2: Use regular Calendar View ICS Exports
As a workaround, you could create Calendar views representing each of your feeds in the appropriate table and then import those views into an external calendar like Google Calendar using the iCal links (support.airtable.com/hc/en-us/articles/225050348-Integrating-Airtable-with-external-calendar-applications). Google Calendar can be embedded easily on any website and will allow you to show multiple "feeds" on one embed.
This is an option available to all Airtable users by default doesn't require use of my app.