Disclaimer: I am not legally qualified.
The onus on the IEC with respect to proof of residence
The way I read this judgment, 5(c) can be summarised as requiring that the IEC “ensure that the voter is registered in the VD where they are ordinarily resident”. 
In my opinion, 5(c) can be broken down into:
- the Electoral Commission is obliged to obtain sufficient particularity of the voter’s address , , 
- to enable it to ensure that the voter is at the time of registration ordinarily resident in that voting district. , , , 
I find that  &  when compared with  &  are contradictory:
“The IEC is also labouring under a misapprehension, which this judgment should help to dispel, that it is obliged to verify voters’ addresses when they register. That is incorrect. What they are obliged to do is obtain sufficient information from the voter as to their ordinary place of residence, to ensure that they are registered in the correct voting district and correct ward.” 
“the IEC must endeavour to ascertain from the person coming to register an address, where they have a physical address, or some detail that will serve as an address for the purposes of the roll. But if there is none then, provided they are registered in the correct ward, they must be registered and the absence of an address does not affect the validity of the voters’ roll.”  (The judgement may erroneously be referring to “ward” here instead of “voting district”).
“That obligation may not have required the chief electoral officer to undertake an investigation of the accuracy of the address given (although, in a society where one cannot lawfully acquire a mobile phone without providing such proof, one wonders why not), but it certainly required that the information given in regard to the voter’s ordinary place of residence had to be sufficiently clear to ensure that the voter could be accurately placed in the correct voting district. A generic address, whether that of an informal settlement, such as Crossroads in Cape Town or Bester’s Camp in Durban, or that of an upmarket suburb, such as Constantia in Cape Town or Morningside in Durban, is simply insufficient for this purpose.” 
“When a voter comes to register as such, it is for the IEC and its officials to procure as much information from that voter as is necessary to enable it to perform its statutory obligation and ensure that the voter is registered in the correct voting district and hence, for the purpose of municipal elections, in the correct ward. In almost all cases this will be relatively easy but in some instances it will present challenges. It is the IEC’s responsibility to resolve those challenges.” 
If a generic address  is not considered sufficient, then how can no address  be considered acceptable?
While I do not believe that the IEC could be reasonably expected to verify the address of every person registering to vote, and neither does the Judgment, registrants will have to provide enough information to make it clear where they are ordinarily resident and where they should be registered. Whatever this information is – whether an address or not, should be recorded.
Indeed, the IEC cannot meet its obligations in 5(c) if it has no detail whatsoever upon which to base its decision to register a person in a particular voting district.
Providing voter addresses to candidates
My reading of 5(d) can be summarised as reminding the IEC that is obliged to comply with the Electoral Act, 16(3) in particular. 
In my opinion, the specific wording of 5(d) in the judgement fits the by-election related context of the case – and provides clarity with respect to to 16(3) in that context. ,
However, it also re-asserts that the IEC is obliged to comply with 16(3) in full. This assertion seems to be supported by the IEC’s own pre-emptive remarks to the effect of provides addresses in all future voters rolls supplied to “contestants”.
What is of specific relevance to political parties is that 16(3) naturally follows from 16(2), and 16(1) and their applicability is thus also reasserted by this judgement.
The specific value is that 16(3), when read with 16(2) and 16(1) compels the IEC to:
- provide a copy of the Voters’ Roll
- as it exists at that time
- including addresses where available , 
- to any person or any political party contesting the elections
- who [have] paid the prescribed fee
Thus, any person or political party contesting the elections should at any time be able to request the Voters’ Roll as it exists at that time and be supplied with a copy that includes addresses where available. 
Noteworthy sections of the judgement
“To construe section 15 in the restrictive fashion suggested by the IEC might advance bureaucratic interests, but it is not consistent with its broader obligation to create an environment in which free and fair elections can take place in which all qualified citizens may participate either as candidates or voters.” 
“The applicants’ right to relief is not constrained by the need to show that the result of the election would have been materially different had the incorrect registrations not occurred.” 
“In August this Court stressed the importance of permitting all citizens to vote in the absence of any justifiable limitation of that right. It accordingly set aside the failure by the chief electoral officer to register prisoners so as to enable them to vote.” 
“The applicant was entitled . . . to stand for election in fair and democratic conditions, regardless of whether ultimately he won or lost.” 
“The focus must be on the impact that this had on their exercise of the right to stand for public office. It is not on whether they would have won or lost had the arrangements for the by-elections been different and not suffered from the flaws of which they complain, but on whether they were seriously hampered in their participation in the electoral process.” 
“All that can safely be said is that the independent candidates were constrained to fight these by-elections under the shadow of uncertainty occasioned by the registration of an unknown number of voters who were not entitled to vote and an inability to identify who these were or to do anything about it.” 
“For example, in a national election, the fact that voters, otherwise qualified to vote, are registered in the incorrect voting district, may be of less significance than in a municipal by-election. But late delivery of voters’ rolls, or delivery of rolls with important information missing, may assume even greater significance at the national than the local level.” 
“These seven by-elections fail that test. They were conducted against the background of fears that voters had been wrongly registered in wards where they were not ordinarily resident and not entitled to vote. It transpired that these fears were well founded. The IEC has proffered no satisfactory explanation for this occurring, seeking instead to shelter behind a contention that it is not obliged to verify voters’ addresses. […] All that can be said is that an election conducted when there is a serious question as to the reliability of the voters’ roll cannot be described as free and fair.” 
“But it is unnecessary in the light of section 16(3) to reach a firm conclusion on this question and I would hesitate to do so without further enquiry into the electoral systems of other democratic countries and the requirements for the preparation of voters’ rolls there. Here, the IEC was in breach of its obligations under section 16(3) of the Electoral Act in not furnishing segments of the voters’ roll with addresses where those were available.” 
“Overall the balance must come down on the side of electoral integrity.” 
“The only other problem mentioned by the IEC is that we are approaching the Christmas holiday period and people may go away. But it rejected that as a ground for postponing the December by-elections in 2013, so it should not be able to rely on it now.”