Well... its the same as asking whether setting up a wireless network within your house is legal. As far as you use the designated frequency bands and don't exceed the transmission power (EIRP on Wikipedia and also MyBroadband article) I can't see why it isn't. There was something a while ago about requiring certain ICASA licenses, but from what I can gather it only applies whenever a wireless network is used for commercial purposes, which WUGs strictly forbid (see http://mybroadband.co.za/vb/showthread.php/143937-Vans-license-holders-enables-WUGS-to-go-commercial)
With regards to Tweaks question, I'm not sure. Since it is only between two friends and no money is going to be exchanged, I guess it should be OK. He said he's also sharing it with his office, so I'm not so sure about that.
With regards to Tweaks question, I'm not sure. Since it is only between two friends and no money is going to be exchanged, I guess it should be OK. He said he's also sharing it with his office, so I'm not so sure about that.