Apple HFS and HFS+ filesystems support file flags containing optional metadata, including the "user immutable" flag which prevents a file from being modified (regardless of Unix permissions.) Mac OS X software routinely sets the user immutable flag when setting files read-only. While Teamprise clients frequently set files read-only, clients do not set the user immutable bit by default to support legacy applications which do not understand the immutable bit.
Using the user immutable flag to set files read-only may be beneficial for certain applications. The Windows File Sharing server included with Mac OS X, for instance, uses the user immutable bit to mark files as read-only.
To enable the user immutable bit on read-only files, set the environment variable TP_SET_IMMUTABLE to the value on.
For information on setting environment variables for your operating system, see Defining an Environment Variable.
This environment variable is ignored on platforms except Mac OS X.