why set app as internal package?

I want to use relay in my own xds server, I found all the core libs are internal.
is it necessary to do this , at least need move server package out of internal

No files or tests are named. Start by mapping the internal packages used by the server and reviewing Go's internal package visibility rules; determine which server APIs must become public and what compatibility boundary is appropriate. Done means the server can be imported by an external xDS server without relying on internal packages, with relevant tests updated or added.

Written by the indexing model from the issue text.