What does this mean: 4yourself or 2others?

You are using the received open source software only for yourself (4yourself), if you as a person do not pass it to other entities like persons, organizations, companies etc., or if you - as a member of a specific development group - pass it only to the other members of your development group. But if you store open source software on any device such as a mobile phone, an USB stick, etc. or if you attach it to any transport medium like email etc. and if you then sell, give away, or simply send this device or  transport medium to anyone (other than a direct member of your development group) then you indeed handover the open source software to third parties (2others).