Is it possible to use one license file on multiple computers? My friend doesn't have internet, so he can't activate online, and I want to share Unity with him, but I think that licenses are locked to one computer. Can I share a license or do I have to request a seperate free license for him?
It's not clear if you mean mean the Pro version or Free version. Pro is licensed per-seat, so I'd say no. The Free version he can use it, but with his own license. If the problem is manual activation, then take your pick:
Manual/Offline Activation of Unity
Also, you may want to read the License:
"Subject to the terms below (the 'Agreement'), Unity Technologies ApS hereby grants you a non-exclusive, non-transferable license to install and to use Unity or Unity Pro or Unity Educational (the 'Software')."
"Except during the trial period, the Software must not be used without a valid license. A license of the Software must only be used on one computer simultaneously. A license of the Software may be installed on a total two computers or virtual machines simultaneously."