Libertas grata est, sed salus quoque servanda est.

Both are nominative singular. They are the subjects of their clauses:

• Libertas grata est = Freedom is welcome / pleasing
• salus quoque servanda est = safety too must be preserved

Both nouns are feminine, third-declension nouns.

Because grata agrees with libertas.

In Latin, adjectives must agree with the noun they describe in:

• gender
• number
• case

Libertas is feminine singular nominative, so the adjective must also be feminine singular nominative: grata.

No. Here grata means something like welcome, pleasing, or dear.

That can confuse English speakers because gratus, grata, gratum is related to the idea of pleasing or thankful, but in a sentence like this:

• Libertas grata est

the meaning is Freedom is welcome / dear / pleasing, not Freedom is grateful.

Quoque means also or too.

It usually comes after the word it emphasizes. So:

• salus quoque = safety too / safety also

That is why the Latin does not put it before salus. English often says also safety or safety too, but Latin commonly places quoque after the emphasized word.

Servanda est is a very common Latin construction called the passive periphrastic.

It is made from:

• a gerundive: servanda
• a form of esse: est

So:

• servanda est = must be preserved / is to be preserved

The gerundive adds the idea of necessity or obligation, not just simple passive action.

Compare:

• servatur = is being preserved / is preserved
• servanda est = must be preserved

Because servanda agrees with salus.

The base verb is servo, servare = to preserve, save, protect.
Its gerundive is:

• servandus masculine
• servanda feminine
• servandum neuter

Since salus is feminine singular nominative, the form must be servanda.

So:

• salus servanda est = safety must be preserved

Because each half of the sentence has its own predicate:

• Libertas grata est
• sed salus quoque servanda est

In the first clause, est is a normal linking verb:

• libertas
  • grata
    • est

In the second, est helps form the passive periphrastic:

• salus
  • servanda
    • est

Latin can sometimes omit est, but here repeating it makes the structure clear and balanced.

Sed is a conjunction meaning but.

It connects the two ideas:

• Freedom is welcome
• but safety also must be preserved

So the sentence sets up a contrast or balancing statement: freedom is valuable, but safety matters too.

Yes.

• libertas, libertatis = freedom, liberty
• salus, salutis = safety, welfare, well-being

Both are feminine third-declension nouns.

That is useful to know because their endings are not as predictable for beginners as first- or second-declension nouns.

Yes. Salus can mean several related things, depending on context:

• safety
• well-being
• health
• welfare
• sometimes even salvation

In this sentence, safety or welfare fits best. Latin words often have a broader range of meaning than a single English translation.

With the passive periphrastic, Latin often uses the dative of agent.

For example:

• nobis salus servanda est = we must preserve safety
  literally, safety is to be preserved by us

So if no person is named, as in your sentence, the obligation is left general or impersonal:

• salus quoque servanda est = safety too must be preserved

It is fairly natural Latin word order, but it also gives a neat rhetorical balance:

• Libertas grata est
• sed salus quoque servanda est

The first clause is simple: subject + adjective + est.
The second mirrors it, but uses the stronger necessity construction servanda est.

Also, placing quoque right after salus emphasizes that safety too deserves attention.