Currently a screen share can only be initiated the Biba app on a Mac or Windows desktop, but it can be viewed by anyone with an internet connection - even if they don't have Biba.
Mobile and Desktop Attendees with Biba
Those already attending the meeting on Biba will either be alerted that a screen is being shared, and can ignore or join (Mobile), or the shared screen will simply pop up (desktop).
For users on the mobile app, the screenshare will cover the roster, but they will still be able to access mute (for themselves) or speakerphone. If they need to access any other controls, they can dismiss the screenshare by tapping the top left corner, then bring it back via a View button at the bottom of the roster.
Dialed in Attendees without Biba
Even if your meeting attendees don't have a Biba account, they can still use your conference PIN code and screenshare link to dial into the call and view any shared screens on their browser. As long as a screen is being shared, attendees can click the link and view the screenshare.
Attendees Joined by PIN
If your meeting attendees aren't Biba users, but need to share their screen during the meeting, they can dlownload Biba, and from the sign in screen they can choose the Join by PIN option. This will allow them to use the organizer's PIN code to join the meeting on Biba and have limited access to Biba features such as screenshare and video, even if they don't have an account.