Hi squeezypeas,
Have you got a copy of the TCL book
http://tinycorelinux.net/~curaga/corebook.pdf, some very useful info in here in relation to creating extensions, although it's based on the x86 version.
In simple terms, extensions, .tcz files, are loaded during the boot process, if their name is included in the onboot.lst file and they exist in the optional directory. To run a startup script add a entry for it in the /opt/bootlocal.sh file, or /opt/bootnetwork.sh if it requires network access.
My understanding of the use of
'startup scripts' in
/tmp/package/usr/local/tce.installed is that they are used to manage extension loading functions, such as placement of default configuration files etc, rather than actually starting the application, as other necessary extensions may not have been loaded at that time, or the system may not yet be fully functionally.
HTH
Jon