For each external asset, retain its source, license or agreement, purchase record where relevant, and the version used. Note any attribution or distribution conditions. A file found online or included in an old project is not automatically available for a new commercial release.
Review the intended use
The relevant questions can include embedding in a game, redistribution of source files, advertising, merchandising, modification, and transfer to another developer. Do not assume that permission for one use settles every later use. Important or unclear terms deserve confirmation from the provider or qualified legal advice.
Keep original assets distinct from edited versions so the relationship remains traceable. If an asset is replaced, update the inventory and check that obsolete files are not still packaged into the build.
At handover, explain which dependencies need a separate account, subscription, or license. The business should know what it can maintain and transfer. A clear record does not provide legal clearance by itself, but it gives the responsible people the information needed to assess the project. Attractive art and working code are only part of a release that another team can use responsibly.