Yes, downloading the Avacus app, creating a wallet, and using its features are all free of charge on the app's side. You can use Avacus at no cost.
That said, there are certain situations where fees may be charged by blockchain networks or third-party services.
Situations where fees apply
Gas fees when sending tokens, etc. (network fees)
When sending tokens or NFTs, a gas fee is required for the blockchain network you're using (such as Ethereum or BNB Smart Chain). This fee is paid to the blockchain network itself, not to Avacus.
Fees when using DApps and DEXs
When using external DApps or DEXs such as Uniswap through the in-app browser, those services and their associated smart contracts may set their own fees. Any fee information shown within Avacus is for reference only.
On-chain actions on SNS, such as the follow feature
Actions that involve an on-chain record, such as following someone in the SNS feature, require a gas fee. Following is optional, however, so no fee is charged if you choose not to follow anyone.
Because Avacus is a non-custodial wallet, you are responsible for keeping enough balance (such as ETH or BNB) in your own wallet to cover any fees.
Related article: What is a Gas Fee?