This is a mixture between new behaviour and an issue in Toad.
Old versions of Team Coding used to make objects read-only if someone else had them checked out.
Now, Toad doesn't make anything read-only. Instead, if you try to compile and you don't have the object checked out, you will be prompted to check out. In this example, since the object is already checked out by another user, Team Coding is preventing compilation.
If you open the output window you will see the output message like the following:
12:59:17 Output: Package TEST.TKD_ADMIN is locked by . Team Coding prevented compilation.
What Toad should do in this case is present a pop-up message, rather than sending the message to the output window (at time of compilation) so that it's clearer.
Waiting for fix in a future release of Toad for Oracle