We have Office 365 E3 SharePoint sites, and I'm wondering if we invite a group of external experts to edit content on this site, do they need to have a license?  We are asking them to sign up with Outlook.com as part of the invitation process.

I'm thinking that the answer is "no" since I can't see such a provision listed in the documentation, but I'm just double-checking.

John

No, they do not need to have a license, and you can invite "unlimited" external users whose doesn't associate to your company, read the limitation and boundaries statement.

https://support.office.com/en-za/article/SharePoint-Online-and-OneDrive-for-Business-software-boundaries-and-limits-8f34ff47-b749-408b-abc0-b605e1f6d498?ui=en-US&rs=en-ZA&ad=ZA

Do note that the external users will have limited features as compared to a paid users,

https://support.office.com/en-us/article/Manage-external-sharing-for-your-SharePoint-Online-environment-c8a462eb-0723-4b0b-8d0a-70feafe4be85