Net omdat oudisies begin, beteken dit nie dat gemeenskapskore optree nie.

Here, net omdat is best understood as just because.

So:

• omdat = because
• net omdat = just because

It introduces the idea the mere fact that X is true does not mean Y is true.

So the sentence is using a very common pattern:

• Net omdat X, beteken dit nie dat Y nie.
• Just because X, it does not mean that Y.

Afrikaans follows a verb-second pattern in main clauses.

Because the sentence begins with the clause Net omdat oudisies begin, that whole clause takes the first position. After that, the finite verb of the main clause must come next:

• Net omdat oudisies begin, beteken dit ...

So the order is:

1. fronted clause: Net omdat oudisies begin
2. finite verb: beteken
3. subject: dit

If you started directly with the main clause, then you would get:

• Dit beteken nie dat gemeenskapskore optree nie.

Both patterns are normal; the first just foregrounds the just because... part.

Dit is the subject of the main clause, and in this kind of structure it works a lot like English it in:

• It does not mean that ...

So:

• beteken dit nie = does it not mean / it does not mean

Even though the sentence starts with a clause, the main clause still needs its subject, and that subject is dit.

This is the normal Afrikaans double negation pattern.

In many negative sentences, Afrikaans uses:

• one nie earlier in the clause
• another nie near the end of the clause

So:

• beteken dit nie dat gemeenskapskore optree nie

This is standard Afrikaans grammar, not extra emphasis.

A rough pattern is:

• Hy kom nie vandag nie. = He is not coming today.
• Dit beteken nie dat ... nie. = It does not mean that ...

Because the thing being negated is beteken:

• it does not mean that ...

The sentence is not saying that community choirs do not perform.
It is saying that the first fact does not automatically lead to that conclusion.

So the negation belongs to the main clause:

• beteken dit nie ... nie

The dat clause itself is positive:

• dat gemeenskapskore optree = that community choirs perform

Dat here means that and introduces a subordinate clause.

So:

• beteken dit nie dat gemeenskapskore optree nie
• does it not mean that community choirs are performing

It links the idea after beteken to the main clause.

Good question. Optree is a separable verb:

• dictionary form: optree
• literal parts: op
  • tree

In a main clause, it often splits:

• Gemeenskapskore tree op. = Community choirs perform.

But in subordinate clauses and infinitive-like environments, it usually stays together:

• dat gemeenskapskore optree

So the reason it is optree here is that it appears inside a dat clause.

Here optree means perform, especially in a musical or stage sense.

Possible meanings of optree in other contexts include:

• perform
• appear on stage
• act
• behave

But with gemeenskapskore (community choirs), the meaning is clearly perform.

No. Afrikaans verbs do not usually change form for person or number in the present tense.

So you get:

• Die oudisie begin. = The audition begins.
• Die oudisies begin. = The auditions begin.

The verb stays begin in both cases.

This is much simpler than English, where you have begin vs begins.

Yes. Afrikaans very often writes compounds as a single word.

So:

• gemeenskap = community
• koor = choir
• gemeenskapskoor = community choir
• gemeenskapskore = community choirs

Notice also that the plural is on the second part:

• koor → kore
• gemeenskapskoor → gemeenskapskore

This kind of compounding is extremely common in Afrikaans.

Yes. After omdat, Afrikaans uses subordinate-clause word order, where the finite verb goes to the end.

In your sentence:

• omdat oudisies begin

Since begin is the only verb, it comes at the end of that clause.

With a longer clause, this is easier to see:

• omdat die oudisies vandag begin
• because the auditions begin today

And with more than one verbal element:

• omdat die oudisies vandag begin het
• because the auditions started today

So yes, omdat triggers subordinate word order.

Yes — this is a very useful pattern:

• Net omdat X, beteken dit nie dat Y nie.
• Just because X, does not mean that Y.

Examples:

• Net omdat hy glimlag, beteken dit nie dat hy gelukkig is nie.
  Just because he is smiling does not mean that he is happy.

• Net omdat dit duur is, beteken dit nie dat dit goed is nie.
  Just because it is expensive does not mean that it is good.

If you remember this frame, you can reuse it in many situations.