I’m not sure what do you mean by the words above… moddb.com says it is “Final latest version of the UDK by Epic, the February 2015 release. Unreal Development Kit is the free edition of Unreal Engine 3…” anything wrong here? is UDK not using c++?
As far as I can guess from your unclear (to me) words, you mean there is more complete version of UDK, and that’s not free, but also includes source-code. But I don’t need source code of UDK (be that free or not). I just need final free version of Unreal Engine, of any version, which can run more or less fine on my laptop with 4GB ram (it can’t be upgraded). so UDK (v3) seems to be ok for my hardware at present. Sooner or later I’ll upgrade, sure…
GGBotnet, thank you 
(in Russian we’ld says for thank you “spasibo”, which originates from words “spasi Bo(h)”, which means “save (you), God”, or more precisely, “let God save you”. don’t know if “thank you” may mean something like that in English)