Dont see their neighbour countries playing in their competitions. Namibia and Zimbabwe play from u13 to senior level in SA provincial competitions.
So is that the only possible thing a country can do to assist their neighbours, is have them play in their local competitions? Tyranny of distance in the pacific islands is a lot more prohibitive then it is to travel between Zimbabwe/Namibia and South Africa.
The All Blacks are actually playing a test match against Samoa in Samoa in 2015, that will be a massive boost for rugby union in the country, arguably the biggest event in the past 20years.
Fiji, Samoa and Tonga play in the Pacific Rugby Cup against Australian and New Zealand Super Rugby teams, rotating between an Australian, Kiwi and Pacific Islands series.
New Zealand regularly send development tours for the New Zealand Maori over to play in Japan, again a boost for the development of rugby in this country.. And i think the NZRU contribution to the development of rugby in the USA has been well documented.
So yes, the NZRU are doing things to assist their neighbours, its not just South Africa. ARU are also helping, admittedly not nearly as much as they ought to be.